Driving apparatus

ABSTRACT

A geared motor  101  comprising a reduction gear unit  102  of oscillating internal meshing planetary gear structure type and a motor unit  103  coupled to each other, the reduction gear unit  102  having a first shaft  111  and a second shaft  112  located on its center axis L, external gears  115   a  and  115   b  being fitted on the outer periphery of the first shaft so as to be capable of oscillating rotations, an internal gear  120  with which the external gears mesh internally being provided concentrically with the first shaft, the second shaft being coupled to the external gears via means  117  for extracting the rotational components of the external gears. A simple planetary roller mechanism  202  for transmitting rotational power by means of the friction between rollers is interposed between the reduction gear unit and the motor unit to reduce the vibration and noise levels greatly.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention particularly relates to a driving apparatushaving an oscillating internal meshing planetary gear structure as itsspeed change mechanism, such as a geared motor.

[0003] 2. Description of the Related Art

[0004] Conventionally, oscillating internal meshing planetary gearing iswidely known which has an internal gear and an external gear internalmeshing with the internal gear, the center axis of the internal gearlying inside the periphery of the external gear [the gearingcorresponding to International Patents Classification (IPC) F16H 1/32].

[0005]FIG. 22 shows an example of a geared motor that has conventionaloscillating internal meshing planetary gearing of this type as itsreduction gear unit, which is described in Japanese Patent Laid-OpenPublication No. Hei 5-231482. This geared motor 1 includes theabove-mentioned reduction gear unit (oscillating internal meshingplanetary gear unit) 2 and a motor unit 3 connected and integrated witheach other.

[0006] The reduction gear unit 2 has a casing 51 which is composed of acentral casing 52 disposed at the axial center, a joint casing 53 on theside closer to the motor unit 3, and a front casing 54 on the sideopposite from the motor unit 3. The motor unit 3 has a casing 55 whichis composed of a cylindrical casing 56 having a stator and the likearranged inside, the joint casing 53 on the side closer to the reductiongear unit 2, and a rear cover 57 on the side opposite from the reductiongear unit 2. Here, the above-mentioned joint casing 53 comprises bothparts of the casings 51 and 55 for the units 2 and 3. Accordingly, theunits 2 and 3 are integrally connected with each other through the jointcasing 53.

[0007] The reduction gear unit 2 has first and second shafts 11 and 12serving as input and output shafts, respectively. Both the shafts arealigned on the center axis L of the unit. The first shaft 11 is disposedon one axial end of the reduction gear unit 2. The second shaft 12 is onthe other axial end of the reduction gear unit 2.

[0008] Two eccentric bodies 13 a and 13 b are fitted on the outerperiphery of the first shaft 11 so as to axially adjoin each other witha given phase difference therebetween (180°, in this example). Theseeccentric bodies 13 a and 13 b make rotations together with the firstshaft 11. The respective centers of the eccentric bodies 13 a and 13 bare a given eccentricity off the axis of the first shaft 11. Externalgears 15 a and 15 b are fitted onto the outer peripheries of theeccentric bodies 13 a and 13 b via bearings 14 a and 14 b, respectively.

[0009] The plural rows of external gears 15 a and 15 b fitted on theeccentric bodies 13 a and 13 b are provided with a plurality of innerpin holes 16 a and 16 b, respectively. Inner pins 17 are fitted to theinner pin holes 16 a and 16 b with some play.

[0010] The external gears are provided in two (in plural rows) mainlyfor the sake of enhancing the transmission capacity, maintaining thestrength, and keeping the rotational balance.

[0011] On the outer peripheries of the external gears 15 a and 15 b areprovided outward teeth each having a trochoidal tooth profile or acircular arc tooth profile. These outward teeth come into internal meshwith an internal gear 20 that is provided concentrically with the firstshaft 11. The internal gear 20 is integrally formed on the innerperiphery of the central casing 52. Each inward tooth of the internalgear 20 is formed with an outer pin 21 held on the inner periphery ofthe central casing 52.

[0012] The result is that the reduction gear unit 2 is characterized byhaving the internal gear 20 and the external gears 15 a, 15 b internallymeshing with the internal gear 20, the center of the internal gear 20lying inside the peripheries of the external gears 15 a, 15 b (thecharacteristic prescribed in IPC F16H 1/32).

[0013] The two external gears 15 a and 15 b are interposed between apair of support carriers 23 and 24. These carriers 23 and 24 arerotatably supported by bearings 31 and 32 fitted to the innerperipheries of the joint and front casings 53 and 54, respectively. Thecarriers 23 and 24 are also integrally connected with each other by aplurality of carrier pins (coupling pins) 25 and spacers 26 piercingthrough the external gears 15 a and 15 b.

[0014] The inner pins 17, fitted to the inner pin holes 16 a and 16 b inthe above-mentioned external gears 15 a and 15 b with some play, areconnected at both ends with the carriers 23 and 24 on both sides so asto be capable of sliding rotations. This allows only the rotationalcomponents of the external gears 15 a and 15 b to be transmitted throughthe inner pins 17 to the carriers 23 and 24 on both the sides.

[0015] The carrier 23 closer to the motor unit 3 is of annular shapehaving a center hole 23 a. One end of the first shaft 11 lies inside thecenter hole 23 a so that the end can be coupled to a motor shaft 61.

[0016] The other carrier 24 is integrally formed on the base of thesecond shaft 12, and has a recess 24 a into which the other end of thefirst shaft 11 is inserted. A bearing 33 is fitted to the innerperiphery of the central hole 23 a in the carrier 23, and a bearing 34is fitted to the inner periphery of the other carrier 24. The firstshaft 11 is rotatably supported by the bearings 33 and 34.

[0017] The motor shaft 61 of the motor unit 3 is supported at its rearend by a bearing 62 and at its front end by a bearing 63. The bearings62 and 63 are fitted to the rear cover 57 and the joint casing 53,respectively. Here, the motor shaft 61 is aligned to be coaxial with thecenter axis L of the reduction gear unit 2.

[0018] The extremity of the motor shaft 61, projected outward from thefront-side bearing 63, is inserted into the reduction gear unit 2.Within the center hole 23 a in the carrier 23 of the reduction gear unit2, the extremity is coupled to the end of the first shaft 11 mentionedabove via a coupling 70.

[0019] In this case, splines are formed in the inner periphery of thecoupling 70 and the outer peripheries of both shafts 11 and 61 so thatthe shafts 11 and 61 come into spline connection with each other throughthe coupling 70. Here, the splines establish the floating connectionbetween the first shaft 11 and the motor shaft 61 while allowingrelative radial play therebetween.

[0020] Now, description will be given of the operation of this gearedmotor.

[0021] In the geared motor 1 of such constitution, one rotation of thefirst shaft 11 coupled to the motor shaft 61 makes one rotation of theeccentric bodies 13 a and 13 b. This one rotation of the eccentricbodies 13 a and 13 b urges the external gears 15 a and 15 b to oscillateand rotate about the first shaft 11. However, since their free rotationson the axis are restricted by the internal gear 20, the external gears15 a and 15 b almost exclusively make oscillations while internalmeshing with this internal gear 20 (this

[0022] is a characteristic of speed reduction structures of this type)Now, assuming that the number of teeth on the respective external gears15 a, 15 b is N and the number of teeth on the internal gear 20 is N+1,the difference between the numbers of teeth is “1.” On that account,each rotation of the input shaft 1 shifts (rotates) the external gears15 a and 15 b by the amount corresponding to one tooth with respect tothe fixed internal gear 20. This means that one rotation of the firstshaft 11 is reduced to −1/N rotations of the external gears 15 a and 15b.

[0023] The oscillating components in the rotations of the external gears15 a and 15 b are absorbed by the clearances between the inner pin holes16 a, 16 b and the inner pins 17. Thus, only the rotational componentsare transmitted via the inner pins 17 to the carriers 23 and 24, andthen to the second shaft 12.

[0024] This consequently achieves speed reduction of −1/N in reductionratio (here, the negative sign represents a reverse rotation).

[0025] Next, description will be directed to another conventionalexample.

[0026]FIGS. 23 and 24 show an example of a conventional geared motordescribed in Japanese Patent Laid-Open Publication No. Hei 10-299841.This geared motor 500 uses an oscillating internal meshing planetarygear structure of so-called power-distributed shaft type. This internalmeshing planetary gear structure comprises a first shaft 502,power-distributed shafts 503, eccentric bodies 504, external gears 505,an internal gear 506, and a second shaft 507. The first shaft 502 is tobe coupled to an external motor shaft 501. The plurality ofpower-distributed shafts 503 are arranged on the circumference of acircle concentric with the first shaft 502, and make revolutions inresponse to the first shaft 502. The eccentric bodies 504 are arrangedon the plurality of power-distributed shafts 503 on a one-on-one basis.The external gears 505 are fitted on the eccentric bodies 504 so as tobe capable of eccentric rotations with respect to the first axis 502.The internal gear 506 is arranged to be concentric with the first axis502. The above-described external gears 505 come into internal mesh withthe internal gear 506 while making the eccentric rotations with respectto the first shaft 502. The second shaft 507 is coupled with theplurality of power-distributed shafts 503. In this internal meshingplanetary gear structure, the eccentric bodies 504 are interposedbetween a pair of support carriers 523 and 524, and thepower-distributed shafts 503 are rotatably supported by the carriers 523and 524. In addition, the above-mentioned first shaft 502 is providedwith a sun roller 511. A plurality of power-distributed rollers 512 formaking external contact with the sun roller 511 are put into splineconnection with the plurality of power-distributed shafts 503 on aone-on-one basis. Around these plurality of power-distributed rollers512 is arranged a press-contact ring 513 which has an inner diametersomewhat smaller than the sum of the diameter of the above-mentioned sunroller 511 and the value twice the diameter of the power-distributedrollers 512. The power-distributed rollers 512 make internal contactwith the press-contact ring 513. Here, the press-contact ring 513 hasthe function of creating contact forces between the sun roller 511 andthe power-distributed rollers 512, which is different from that of thering in a simple planetary structure.

[0027] This kind of gear structures as shown in FIGS. 22 and 23 aredivided into two types: namely, a type in which external gears makeoscillating rotations with respect to internal gears as described above,and the contrasting type in which internal gears make oscillatingrotations with respect to external gears.

[0028] By the way, with the recent development of industries, theincreasing variety of user needs has grown the demand for drivingapparatuses which can offer yet higher reduction ratios (for example,reduction ratios equal to or higher than 1/200) with compactconfigurations. FIG. 28 shows a driving apparatus of two stage type,having been proposed in response to these needs.

[0029] This driving apparatus 1001 has an additional reduction mechanismunit interposed between its reduction mechanism unit and drive unit tomake higher reduction ratios up to about 1/1000 attainable.Specifically, the driving apparatus 1001 comprises: a drive unit (motor)1002 for generating rotational power; a first reduction mechanism unit1004 coupled to the drive unit for rotational power transmission; and asecond reduction mechanism unit 1006 of internal meshing planetary gearstructure, coupled to the first reduction mechanism unit for rotationalpower transmission.

[0030] The second reduction mechanism unit 1006 in the driving apparatus1001 has a first shaft (input shaft) 1011 to be coupled to the firstreduction mechanism unit 1004, and a second shaft 1012 arranged to becoaxial with the first shaft 1011 to make the output shaft. Twoeccentric bodies 1013 a and 1013 b are fitted on the outer periphery ofthe first shaft 1011 so as to axially adjoin each other with a givenphase difference therebetween (180°, in this example). These eccentricbodies 1013 a and 1013 b make rotations together with the first shaft1011. The respective centers of the eccentric bodies 1013 a and 1013 bare a given eccentricity off the axis of the first shaft 1011. Externalgears 1015 a and 1015 b are fitted on the outer peripheries of theeccentric bodies 1013 a and 1013 b via bearings 1014 a and 1014 b,respectively.

[0031] The plurality of external gears 1015 a and 1015 b fitted on theeccentric bodies 1013 a and 1013 b are provided with a plurality ofinner pin holes 1016 a and 1016 b, respectively. Inner pins 1017 arefitted to inner pin holes 1016 a and 1016 b with some play.

[0032] The external gears are provided in two (in plural rows) mainlyfor the sake of enhancing the transmission capacity, maintaining thestrength, and keeping the rotational balance. The plural-rowconfiguration is particularly preferable when this structure is appliedto the subsequent stage of a two-stage type driving apparatus as in thisexample. The reason for this is that the transmission capacity(transmission torque) increases on the subsequent stage.

[0033] On the outer peripheries of the external gears 1015 a and 1015 bare provided outward teeth each having a trochoidal tooth profile or acircular arc tooth profile. These outward teeth come into internal meshwith an internal gear 1020 which is provided concentrically with thefirst shaft 1011. The internal gear 1020 is integrally formed on theinner periphery of the casing 1051. Each inward tooth of the internalgear 1020 is formed with an outer pin 1021.

[0034] The result is that the second reduction mechanism unit 1006 ischaracterized by having the internal gear 1020 and the external gears1015 a, 1015 b internally meshing with the internal gear 1020, thecenter of the internal gear 1020 lying inside the peripheries of theexternal gears 1015 a, 1015 b (the characteristic prescribed in IPC F16H1/32).

[0035] The casing 1051, explained particularly, is composed of a centralcasing 1052, a joint casing 1053 on the side close to the drive unit1002, and a front casing 1054 arranged on the side opposite from thejoint casing 1053. Thus, this casing 1051 accommodates the secondreduction mechanism unit 1006.

[0036] The two external gears 1015 a and 1015 b are interposed between apair of carriers (supporting carriers) 1023 and 1024. These carriers1023 and 1024 are rotatably supported by two bearings 1031 and 1032fitted to the inner periphery of the casing 1051. Besides, the carriers1023 and 1024 are integrally connected with each other by a plurality ofcarrier pins (coupling pins) 1025 and spacers 1026 piercing through theexternal gears 1015 a and 1015 b.

[0037] The inner pins 1017, fitted to the inner pin holes 1016 a and1016 b in the external gears 1015 a and 1015 b with some play, aresupported at both sides by the pair of carriers 1023 and 1024 so as tobe capable of sliding rotations. This allows only the rotationalcomponents of the external gears 1015 a and 1015 b to be transmitted tothe carriers 1023 and 1024.

[0038] The carrier 1023 closer to the drive unit 1002 is of annularshape having a center hole 1023 a. One end of the first shaft issupported by the center hole 1023 a via a bearing. The other shaft endis supported by another bearing fitted into the carrier 1024 on theopposite side. In short, the first shaft 1011 is rotatably accommodatedin between the pair of carriers 1023 and 1024.

[0039] In this second reduction mechanism unit, one rotation of thefirst shaft 1011 causes the rotation of both the eccentric bodies 1013 aand 1013 b. This urges the external gears 1015 a and 1015 b to oscillateand rotate about the first shaft 1011. However, since their freerotations are restricted by the internal gear 1020, the external gears1015 a and 1015 b almost exclusively make oscillations while internallymeshing with the internal gear 20.

[0040] Assuming that the number of teeth on the respective externalgears 1015 a, 1015 b is N and the number of teeth on the internal gear1020 is N+1, then the difference between the numbers of teeth is “1.”Thus, each rotation of the first shaft 1011 shifts (rotates) theexternal gears 1015 a and 1015 b by the amount corresponding to onetooth with respect to the fixed internal gear 20. The result is that onerotation of the first shaft 1011 is reduced to −1/N rotations of theexternal gears 1015 a and 1015 b.

[0041] The oscillating components in the rotations of the external gears1015 a and 1015 b are absorbed by the clearances between the inner pinholes 1016 a, 1016 b and the inner pins 1017. On that account, only therotational components are transmitted via the inner pins 1017 to thecarriers 1023 and 1024, and finally to the second shaft 1012.

[0042] This consequently achieves speed reduction of −1/N in reductionratio (the negative sign represents a reverse rotation)

[0043] In this driving apparatus 1001, the first reduction mechanismunit 1004 also uses an oscillating internal meshing planetary gearstructure, and has almost the same configuration as that of the secondreduction mechanism unit 1006. For the sake of avoiding repetitivedescriptions, like parts or members in this diagram are thereforedesignated by like reference numerals having the same lower two digits,and their constitutional, operational, and other detailed descriptionswill be omitted here.

[0044] The first reduction mechanism unit 1004 is different from thesecond reduction mechanism unit 1006 chiefly in the provision of asingle (singular row of) external gear 1315. The reason for thedifference seems to be that the preceding stage is smaller intransmission capacity (transmission torque) as compared to thesubsequent stage, so that even a single external gear can well satisfythe strength and other requirements.

[0045] A carrier 1324 on the output side of the first reductionmechanism unit 1004 is coupled to the first shaft 1011 of the secondreduction mechanism unit 1006 by means of a spline structure. A firstshaft 1311 of the first reduction mechanism unit 1004 is coupled to adrive shaft 1061 of the drive unit 1002.

[0046] The casing 1351 for accommodating the first reduction mechanismunit 1004 is composed of a central casing 1352, a joint casing 1353 onthe side closer to the drive unit 1002, and the joint casing 1053 on theside closer to the second reduction mechanism unit 1006. Hence, it isthe joint casing 1053 that integrally connects the first and secondreduction mechanism units 1004 and 1006, and comprises parts of both thecasings 1051 and 1351.

[0047] In the driving apparatus 1001 of the above-describedconstitution, the rotational power from the drive unit 1002 isdecelerated in two steps by the first and second reduction mechanismunits 1004 and 1006 both of oscillating internal meshing planetary gearstructure, and then output though the second shaft 1012.

[0048] By the way, these conventional examples have been facing a commonproblem. That is, a reduction gear unit using this kind of internalmeshing planetary gear structure, in which the external gears (orinternal gear) make(s) relative oscillating rotations with respect tothe mating gear(s), indeed has an advantage in that higher reductionratios can be obtained from the simple, compact, high-rigiditiedstructure. However, such a reduction gear unit inevitably causes ahigh-noise problem due to the configuration that the external gears (orinternal gear) make(s) oscillations while meshing with the matinggear(s).

[0049] In particular, since a reduction gear unit is connected toanother external unit in actual use, these units produce resonance witheach other to cause a problem of yet higher noise production.

[0050] For example, when the reduction gear unit is combined with amotor to constitute a geared motor as described above, the vibrationsproduced from the reduction gear unit vibrate the motor coupled to theunit. These vibrations are then combined with the vibrations generatedby the motor itself to produce complex resonance. Moreover, thesevibrations are sometimes returned to the reduction gear unit to generatemore complex resonance, possibly causing the entire geared motor toproduce extremely high noise.

[0051] In this regard, the geared motors in the above examples havealready been provided with prevention measures against the resonancebetween the motor unit and the reduction gear unit(s) For example, inthe example of FIG. 22, the motor shaft 61 and the first shaft 11 wereput into floating connection with each other via the spline-typecoupling 70 to block the mutual transmission of vibrations between themotor unit 3 and the reduction gear unit 2.

[0052] However, simply establishing a floating connection through theintervention of the coupling 70 could not achieve very successfulsuppression against the mutual transmission of the vibrations, failingto offer a sufficient noise reduction effect.

[0053] Besides, the geared motor of FIG. 23, using the internal meshingplanetary gear structure of power-distributed shaft type, was actuallyoperated and found that it also failed to offer a noise reduction effectas high as expected. The cause for this seems to be as follows:

[0054] In this power-distributed-shaft-typed structure, the respectivepower-distributed shafts 503 are subjected to vibrations and flexureaccompanying the oscillating movements of the external gears 505. Thisinevitably increases the possibility that the power-distributed shafts503 be vibrated or deformed (bent) under the loads from the externalgears 505. Meanwhile, this geared motor still arranges on thepower-distributed shafts 503 the power-distributed rollers 512 which arein press contact with the sun roller 511. As a result, the vibrationsand deformations of the power-distributed shafts 503 are directlytransferred to the power-distributed rollers 512 and then to the sunroller 511, whereby the effect obtained from the use of the frictionrollers, of blocking the vibration transmission, is hampered fromfunctioning successfully. In other words, the assignable cause seems tobe the configuration that the rollers 512 suitable for high-speed,low-torque power transmission are directly arranged on thepower-distributed shafts 503 which undergo the direct influence of thedeformation accompanying the load transmissions in the internal meshingplanetary gear structure.

[0055] In any case (regardless of the cause), the above-describedconventional art, despite the incorporation of frictional rollers, endedup failing to achieve such a profound noise-improving effect as wouldrenew the common knowledge.

[0056] In the meantime, the driving apparatus 1001 shown in FIG. 28 wascapable of achieving extremely high reduction ratios by virtue of thefirst and second reduction mechanism units 1004 and 1006 both ofoscillating internal meshing planetary gear structure. In this respect,the driving apparatus 1001 well satisfied the wide needs of the market.In other words, a feature of this driving apparatus 1001 was that therotational power from the drive unit 1002 can be transmitted to thesecond shaft 1012 of the second reduction mechanism unit 1006 asmaintained in coaxiality to offer extremely high output.

[0057] The driving apparatus 1001, however, was configured so that thenew central and joint casings 1352 and 1353 were interposed between thesecond reduction mechanism unit 1006 and the drive unit 1002 toaccommodate the first reduction mechanism unit 1004. This configurationcaused a great axial extension of the entire apparatus and ended up withconsiderably high manufacturing costs.

[0058] Even in this driving apparatus shown in FIG. 28, both the firstand second reduction mechanism units 1004 and 1006 were of reductiongear structures including gears (external internal gears). Therefore,when coupled to each other, these units produced a problem ofgreatly-increased noises. An assignable cause appears to derive from theconfiguration of simply coupling (linking) the casings 1051 and 1351which have an internal space independent of each other. Here, noisesinside the respective casings are resonated and amplified in both theinternal spaces. Another cause appears to consist in that: like theexamples of FIGS. 22 and 23 described before, the drive units 1002 andtwo reduction mechanism units 1004 and 1006, each having one or morepeak frequencies different from those of the others, are coupled withone another to produce complex resonance phenomena.

[0059] By the way, the approaches to a two-stage reduction typeattaining higher reduction ratios, other than the driving apparatus 1001described above, seems to include the conversion of the first reductionmechanism unit into a parallel axis gear structure having spur gears incombination.

[0060] To attain a high reduction ratio, however, this parallel axisgear structure requires a greater center distance between the input-sidegear (pinion) and the output-side gear so as to establish a largerdifference in the number of teeth between the meshing gears. Then, inresponse to the center distance, the entire driving apparatus isexpected to be greater in radial dimension (along with axial dimension).Besides, in order to make the drive unit (motor) and the output shaftcoaxial with each other, the first reduction mechanism unit itselfrequires two stages of gears (three stages, for the entire apparatus) tocorrect the deviation of the shaft center, inevitably causing axialextension of the apparatus.

SUMMARY OF THE INVENTION

[0061] The present invention has been achieved in view of the foregoingproblems. It is thus an object of the present invention to provide adriving apparatus which comprises an oscillating internal meshingplanetary gear structure capable of great reduction in vibration andnoise levels.

[0062] It is another object of the present invention to provide adriving apparatus which can achieve a reduction ratio higher thanconventionals with greatly-reduced noises while suppressing an increasein size and cost as much as possible.

[0063] The foregoing objects of the present invention have been achievedby the provision of a driving apparatus comprising: an oscillatinginternal meshing planetary gear unit having an internal gear and anexternal gear making internal contact with the internal gear, the centerof the internal gear lying inside the periphery of the external gear;and an external unit coupled to the oscillating internal meshingplanetary gear unit so as to be capable of inputting (or extracting)power thereto (or therefrom). Between the oscillating internal meshingplanetary gear unit and the external unit is interposed a frictionaltransmission unit for transmitting rotational power between theoscillating internal meshing planetary gear unit and the external unitby means of friction among a plurality of friction rollers makingcontact with each other. The friction roller unit is constituted by asimple planetary roller mechanism including the friction rollersconsisting of a sun roller, a plurality of planetary rollers beingretained by a planetary carrier and making rolling contact with theouter periphery of the sun roller, and a ring roller with which theplurality of planetary rollers make internal contact.

[0064] The essence of this driving apparatus consists of two points. Oneis that a frictional transmission unit is interposed between theoscillating internal meshing planetary gear unit and the external unit.The other is that a simple planetary roller mechanism is adopted for thefrictional transmission unit.

[0065] It will become apparent from the following descriptions and testresults that the present invention offers its inherent effect (beyondthe bounds of common knowledge) only after the above-mentioned twopoints are combined with each other. In other words, either of thepoints by itself cannot offer such a beneficial effect.

[0066] Hereinafter, descriptions thereof will be given in furtherdetail.

[0067] In this driving apparatus, initially, the frictional transmissionunit of simple planetary roller structure is interposed between theoscillating internal meshing planetary gear unit and the external unit,and therefore the oscillating internal meshing planetary gear unit islow in input rotational speed in the first place. This allows reductionof the vibrations generated in the oscillating internal meshingplanetary gear unit. In addition, the vibrations being transmittedbetween the units on both sides of the frictional transmission unit (inparticular, the vibrations along the direction of rotation and thevibrations along the axial direction) can be absorbed by the contactsurfaces of the friction rollers in the frictional transmission unit.

[0068] As a result, the complex resonance phenomena resulting from thevibration transmission between the oscillating internal meshingplanetary gear unit and the external unit can be avoided to reduce thelevel of the noises produced by the entire driving apparatus.

[0069] Put another way, since a third unit (the frictional transmissionunit), which may be regarded as a detour circuit for blocking thevibration transmission, is deliberately interposed between theoscillating internal meshing planetary gear unit and the external unit,it becomes possible to effectively suppress both the vibrationtransmissions from the oscillating internal meshing planetary gear unitto the external unit and from the external unit to the oscillatinginternal meshing planetary gear unit, with the result of overall noisereduction.

[0070] Here, what is important is that a simple planetary rollermechanism is adopted for the frictional transmission unit.

[0071] More specifically, the simple planetary roller mechanism employedhere for the frictional transmission unit carries out the rotationalpower transmission by means of the friction among the contact surfacesof rollers, particularly owing to the power transmission structurepeculiar to the simple planetary roller mechanism which involvesrotations and revolutions of the planetary rollers. Therefore, therespective contact surfaces and the portions in which the planetarycarrier supports the planetary rollers can absorb the vibrations (inparticular, those along the direction of rotation and those along theaxial direction) under the mutual transmission between the units on bothsides of the frictional transmission unit (namely, the oscillatinginternal meshing planetary gear unit and the external unit).

[0072] The above-mentioned driving apparatus of power-distributed shafttype shown in FIG. 23 did use friction rollers as well. However, thepower-distributed shaft type did not have the simple planetary rollermechanism, but a structure in which the power-distributed rollers 512sandwiched between the sun roller 511 and the press-contact ring 513were inherently apt to pick up vibrations of the power-distributedshafts 503. Accordingly, with the vibrations and flexure of thepower-distributed shafts 503, the power-distributed rollers 512 madeposition shifts and vibrations to preclude the proper power transmission(without speed fluctuations) with the sun roller 511. The result wasthat the vibrations of the power-distributed rollers 512 themselvesaffected the overall vibrations and noises before the rollers 512fulfilled their vibration absorbing function over the frictional contactsurfaces.

[0073] In other words, this apparatus was not originally based on thephilosophy of resonance avoidance. Therefore, the apparatus had such aconfiguration that the vibrations from the power-distributed shaft 503were directly transmitted to the power-distributed rollers 512 and thento the sun roller 511, and lacked a structure for achieving the objectof the present invention to avoid resonance by suppressing vibrationtransmission.

[0074] On this account, even the incorporation of the friction rollersdid not help achieve a noise-improving effect as profound as would renewthe common knowledge of geared motors. This ended up with a belief that“friction rollers can only offer such an effect at best,” and thedevelopment was discontinued without further scrutiny.

[0075] On the contrary, in the case of the present invention in which asimple planetary roller mechanism is adopted for the frictionaltransmission unit, the power transmission is carried out by means ofrelative movements among the three parties, namely, the sun roller atthe inner side, the ring roller at the outer side, and the planetaryrollers interposed therebetween (instead of the direct powertransmission by means of the power-distributed rollers' rotationsthemselves). On this account, the frictional transmission unit need notundergo unnecessary deformation or vibrations from the oscillatinginternal meshing planetary gear unit directly.

[0076] Hence, even though interposed between the sun roller and the ringroller, the planetary rollers make only rolling contact with the sun andring rollers at a pressure necessary for frictional transmission. Thefrictional contact surfaces are small in pressure fluctuation. As aresult, the vibration transmission through the frictional transmissionunit is suppressed. In addition, the frictional contact surfaceseffectively fulfill their vibration absorbing function as describedbefore to block the mutual vibration transmission among the units,thereby offering a high effect for noise reduction. The adoption of thesimple planetary roller mechanism also permits the input and outputportions of the frictional transmission unit to be arranged coaxiallywith each other. Thus, for example, the coupling portion between the sunroller and the external unit and the coupling portion between theplanetary carrier and the oscillating internal meshing planetary gearunit can be arranged on the same axis.

[0077] This coaxiality particularly means a structure in which theaforementioned loads from the external gears are exerted exclusively onthe single shaft at the central portion of the unit (unlike thepower-distribution shaft type). The coaxiality is therefore beneficialin that simply increasing the rigidity of the central portion canenhance the rigidity of the entire unit. It is also beneficial in termsof vibration block because the vibrations from the external gears can beconcentrated on the single, high-speed shaft, and coupling thishigh-speed shaft to an end of the frictional transmission unit cancomplete the connection with the frictional transmission unit.

[0078] In other words, the simple, compact structure not only is capableof enhancing the rigidity to beneficially allow higher torquetransmission by that much, but also is advantageous in terms of noisereduction.

[0079] This coaxiality is also beneficial in making the presentinvention readily applicable to a geared motor in which the drive shaftof its external unit and the input and output shafts of its oscillatinginternally meshing planetary gear unit are aligned on a single centeraxis. For example, the driving apparatus of the present invention can beeasily realized by adding a frictional transmission unit of theabove-described simple planetary roller mechanism type to between themotor unit 3 and the oscillating internal meshing planetary gear unit 2of the conventional geared motor 1 shown in FIG. 22. In the geared motor1 in FIG. 22, the motor shaft 61 and the first shaft 11 of theoscillating internal meshing planetary gear unit 2 were coupled by thecoupling 70. This coupling 70 may be diverted to couple the carrier ofthe simple planetary roller mechanism and the oscillating internalmeshing planetary gear unit or to couple the shaft of the sun roller andthe drive shaft of the external unit.

[0080] In addition, the adoption of the simple planetary rollermechanism makes it possible to obtain a given reduction ratio at thisstage. Thus, the simple planetary roller mechanism at the precedingstage can be combined with the oscillating internal meshing planetarygear unit at the subsequent stage to achieve higher reduction ratioseasily. Unlike gears, the simple planetary roller mechanism is easy toset the reduction ratio finely. This allows easy provision of a seriesof geared motors with many steps of reduction ratios, or a geared motorhaving a particular reduction ratio corresponding to a specificapplication.

[0081] Here, the torque transmission by means of frictional transmissionat the preceding stage cannot secure as much transmission torque as thetorque transmission by means of gear meshing at the subsequent stagedoes. This, however, makes little difference because of the followingtwo reasons. First, the amount of torque to transmit in thepreceding-stage reduction is inherently rather small. Second, the simpleplanetary roller mechanism, as described later, is adjustable in thetorque for each roller to transmit by choosing the input and outputmembers.

[0082] In particular, the simple planetary roller mechanism can supportits planetary rollers by using a planetary carrier which is separatefrom the members of the oscillating internal meshing planetary gearunit. Accordingly, even when the oscillating internal meshing planetaryunit undergoes some vibrations and deformation, little influence reachesthe roller contact surfaces of the simple planetary roller mechanism.This realizes the torque transmission with reliability and stability,further reducing the possibility of problems arising.

[0083] Now, the driving apparatus of the present invention may be usedwith an external unit connected to either the high- or low-speed shaftside of the oscillating internal meshing structure, or to both. Sincethe highest vibrations are generated at the high-speed shaft side, thepresent invention is particularly effectively applied with an externalunit connected to the high-speed shaft side.

[0084] The external units include machines to be driven, aside fromdrive sources such as a motor. The following are examples of the unitconnection.

[0085] In the case where the oscillating internal meshing planetary gearunit is used as reduction gears, its high-speed shaft side is coupledwith a motor as the drive source, and its low-speed shaft side iscoupled with a machine to be driven. This is the typical usage of ageared motor. In the case where the oscillating internal meshingplanetary gear unit is used as step-up gears, the low-speed shaft sideis coupled with the drive source and the high-speed shaft side iscoupled with the machine to be driven. Then, the present invention isapplied to between units that may produce resonance.

[0086] Specifically, when resonance may occur between the drive sourceand the oscillating internal meshing planetary gear unit in mutualcoupling, the frictional transmission unit is interposed between thedrive source and the oscillating internal meshing planetary gear unit.When resonance may arise between the machine to be driven and theoscillating internal meshing planetary gear unit, the frictionaltransmission unit is interposed between the machine to be driven and theoscillating internal meshing planetary gear unit. By so doing, theoverall vibrations and noises can be reduced.

[0087] The frictional transmission unit accomplishes the powertransmission by means of the friction among the friction rollers. Thus,a desired reduction ratio can be obtained from this unit by properlymodifying the diameters of the friction rollers contacting one another.Frictional transmission, however, is not suitable for high torquetransmission. Therefore, this unit is favorably used, e.g., for thepreceding-stage reduction mechanism in the cases where the oscillatinginternal meshing planetary gear unit is operated for speed reduction. Byso doing, the overall, total reduction ratio can be set at higherlevels.

[0088] Now, the ways to support the planetary rollers in theaforementioned simple planetary roller mechanism includes the followingtwo.

[0089] In one way, the planetary carrier in the simple planetary rollermechanism is provided with a retainer for occupying spaces around theplurality of planetary rollers to retain the planetary rollers atconstant mutual positions (hereinafter, referred to as retainer type).

[0090] In the other, the planetary carrier in the simple planetaryroller mechanism is provided with pins for penetrating through therespective centers of the planetary rollers to retain the planetaryrollers at constant mutual positions (hereinafter, referred to as pintype).

[0091] As for the differences between the retainer type and the pintype, the pin type is superior to the retainer type in: (a) powertransmission efficiency, (b) power transmission stability, and (c)allowance for torsion and mounting errors. The reason for this is thatthe pin type has a structure of fitting the planetary rollers on theouter peripheries of the pins via bearings so that it is easy for theplanetary rollers to maintain higher rotational performance than in theretainer type.

[0092] In addition, the effects (a)-(c) suggest that the pin type alsogenerally offers more favorable properties as to “the vibrationsuppressing effect” for a long term as compared to the retainer type.

[0093] However, as far as “the vibration suppressing effect” isconcerned, there is a possibility of making the retainer type offer abetter effect than the pin type does, depending on the design andmaintenance. The reason for this seems to be that the retainer type, asdescribed later, has the output-extracting retainer which is kept out ofpress contact with the sun roller and the ring roller, or put in a sortof free state, to exclusively receive circumferential driving forcesfrom the planetary rollers. This retainer structure makes it possible toavoid the vibration transmissions through the following two paths:

[0094] a) pins (oscillating-internal-meshing-planetary-gear-unitside)→planetary rollers→sun roller (motor side); and

[0095] b) pins (oscillating-internal meshing-planetary-gear-unitside)→planetary rollers→ring roller (casing side).

[0096] Accordingly, vibrations can be intercepted between theoscillating internal meshing planetary gear unit and the external unitwith yet higher reliability.

[0097] The relationship among the fixed, input, and output elements ofthe simple planetary roller mechanism creates the possible combinationsshown in the table of FIG. 16. To name the combinations:

[0098] 1) With the sun roller as the input element, the ring rollermakes the fixed element and the planetary rollers the output element, orthe ring roller makes the output element and the planetary rollers thefixed element;

[0099] 2) With the planetary rollers as the input element, the ringroller makes the fixed element and the sun roller the output element, orthe ring roller makes the output element and the sun roller the fixedelement; and

[0100] 3) With the ring roller as the input element, the planetaryrollers make the fixed element and the sun roller the output element, orthe planetary rollers make the output element and the sun roller thefixed element.

[0101] The simple planetary roller mechanism prefers that the ringroller make the fixed element, either the planetary carrier forsupporting the plurality of planetary rollers or the sun roller theinput element, and the remaining the output element.

[0102] When the fixed element is thus made of the ring roller arrangedon the periphery, this ring roller has only to be fixed to the casing,thereby allowing rather simple configuration for the mechanism.

[0103] It is also preferable that: the above-mentioned external unit bea motor unit for supplying a rotational input to the oscillatinginternal meshing planetary gear unit; the frictional transmission unitbe interposed between a drive shaft of the motor unit and theoscillating internal meshing planetary gear unit; and the oscillatinginternal meshing planetary gear unit and the motor unit be integrallyconnected with each other by a joint casing comprising parts of thecasings for these units, the frictional gearing unit being arrangedinside the joint casing.

[0104] Given that the external unit is a motor unit, the drive shaft ofthe motor unit is connected to the high-speed shaft side of theoscillating internal meshing planetary gear unit when the planetary gearunit is used as reduction gears. In short, there is constituted atypical geared motor. Then, in such a geared motor, the vibrationamplifying effect resulting from resonance can be avoided by interposingthe frictional transmission unit between the high-speed shaft of theoscillating internal meshing planetary gear unit and the drive shaft ofthe motor unit to block the vibration transmission between the motorunit and the oscillating internal meshing planetary gear unit.

[0105] By the way, in typical composition of a geared motor, the casingof the oscillating internal meshing planetary gear unit and the casingof the motor unit are coupled with each other to form an integratedgeared motor. In conventional cases, both the units are coupled via ajoint casing that comprises a part of the casing of each unit (seeJapanese Patent Laid-Open Publication No. Hei 5-231482).

[0106] Therefore, the newly-added frictional transmission unit can bearranged inside that joint casing to permit its easy incorporationwithout a significant change in the structures of the units on bothsides.

[0107] Of the coupling portions between the frictional transmission unitand the oscillating internal meshing planetary gear unit and between thefrictional transmission unit and the external unit, at least onecoupling portion preferably has a floating connection structure.

[0108] According to this constitution, the shaft coupling portion of thefrictional transmission unit with the oscillating internal meshingplanetary gear unit or the external unit has a floating connectionstructure. Therefore, the vibrations caused by each unit's oscillationscan be prevented from acting on the frictional rollers via the couplingportion, thereby suppressing fluctuations in the contact pressurebetween the friction rollers. This permits the stable, sure torquetransmission with no fluctuations in transmission torque in thefrictional transmission unit.

[0109] Here, it is yet preferable that: of the coupling portions betweenthe planetary carrier in the frictional transmission unit of simpleplanetary roller mechanism and the oscillating internal meshingplanetary gear unit and between the sun roller and the external unit, atleast the coupling portion between the planetary carrier and theoscillating internal meshing planetary gear unit has the floatingconnection structure.

[0110] Specifically, according to this constitution, at least thecoupling portion between the planetary carrier and the oscillatinginternal meshing planetary gear unit is provided with the floatingstructure to minimize the transmission of radial vibrations from theoscillating internal meshing planetary gear unit to the single planetaryroller mechanism in the case where the ring roller of the simpleplanetary roller mechanism makes the fixed element, the planetarycarrier is coupled to the oscillating internal meshing planetary gearunit, and the sun roller is coupled to the external unit. Consequently,further suppression of the mutual vibration transmission between theoscillating internal meshing planetary gear unit and the external unitcan be achieved to avoid the resonance problem.

[0111] The above-mentioned floating connection structure may employ aspline connection structure, for example. This facilitates therealization of the structure, for a floating connection state can beobtained from the splines, a commonly available shaft-couplingstructure.

[0112] Incidentally, other examples of the floating connection structureinclude a gear connection.

[0113] As described above, the relationship among the fixed, input, andoutput elements in a simple planetary roller mechanism have thecombinations shown in FIG. 16. Of these, the constitutions in which thering roller of the single planetary roller mechanism makes the fixedelement with either the planetary carrier supporting the plurality ofplanetary rollers or the sun roller as the input element and theremaining as the output element (the constitutions corresponding to Aand C in FIG. 16) particularly provide various advantages when combinedwith the assembly that utilizes a structure of forming a mountingreference surface.

[0114] That is, when the fixed element is made of the ring rollerarranged on the periphery, it is possible to fix this ring roller ofgreatest dimension to the casing. This basically allows simplerstructures for both the simple planetary roller mechanism and thecasing, and achieves further noise reduction.

[0115] The structure of forming a mounting reference surface ispreferably adopted due to the following reason.

[0116] In its process of contrivance, the driving apparatus according tothe present invention used common assembling means to fix the ringroller to the casing. Specifically, a cylindrical accommodating portionhaving an inside diameter somewhat smaller than the outside diameter ofthe ring roller was formed in the casing, and the ring roller was“press-fitted” and fixed to the accommodating portion. However, testsrevealed that the method of fixing the ring roller by “press-fit” had aconsiderable number of problems. The reason for this seems to be asfollows:

[0117] (1) In view of miniaturization, the ring roller needed to have athickness as small as possible. When such a ring roller was subjected tothe method of fixing by pressing, the ring roller might be deformedradially inwardly. This radially inward deformation could producefluctuations in contact pressure (line pressure) both on the contactsurfaces between the planetary rollers and the ring roller and on thecontact surfaces between the planetary rollers and the sun roller. As aresult, the value of the contact pressure (line pressure) after actualmounting of the ring roller differed from the value of the contactpressure predetermined before the incorporation. In particular, theactual pressure fluctuated in accordance with circumferential positions,thereby precluding smooth rotations/revolutions of the planetaryrollers.

[0118] (2) Under the circumstances where the high-rigidity casingexerted high pressures on the ring roller from radial outsides, themajority of the radial vibrations having been transmitted to theplanetary rollers (through the sun roller or the planetary carrier) weretransmitted as-received to the mating side through the planetary carrieror the sun roller.

[0119] In other words, the ring roller under the press-fitted state hadlittle allowance in bending (distorting) itself slightly in the radialdirection. Thus, in this driving apparatus (under the process ofcontrivance) having the ring roller fixed by press-fit, the majority ofthe radial vibrational energy having been received by the planetaryrollers via the planetary carrier was “directly” transmitted to the sunroller while the majority of the radial vibrational energy having beenreceived by the planetary rollers via the sun roller was “directly”transmitted to the planetary carrier. In particular, a so-called“transmission structure for radial vibrational energy” was formed in thesimple planetary roller mechanism.

[0120] (3) The vibrations having been transmitted to the ring rollerwere then transmitted to the casing with a high possibility of vibratingthe casing.

[0121] That is, after the fixing by press-fit, the vibrations havingbeen transmitted to the ring roller would directly vibrate thecylindrical surface of the roller in radial directions (the direction ofthe thickness) against the casing of generally cylindrical shape.Accordingly, the casing could easily cause resonance, which wastransmitted to the casings of the external unit and the internal meshingplanetary gear unit to induce resonance of the entire driving apparatus.

[0122] However, when the press-fit fixing is abandoned and substitutedwith the assembly by using amounting reference surface, the mountingdeformation of the ring roller resulting from the press-fit can beminimized to maintain the uniformity and stability of the tangentialline pressures. At the same time, vibrations of the ring roller itselfcan be allowed to some extent to achieve energy absorption there. Inaddition, these vibrations can be surely received by the mountingreference surface (of higher rigidity in the radial direction) formedalong the direction of the casing's thickness (or by a surfaceconforming thereto, to be described later) so that the vibrations areprevented from being transmitted directly in the direction of thecasing's thickness.

[0123] In other words, the ring roller can be fixed to the casingwithout undergoing radial pressures, or as pressed against the mountingreference surface perpendicular to the axial direction, to realizesmooth rotations/revolutions of the planetary rollers. Moreover, thering roller's capacity for radial deformation can provide a radialvibration absorbing function to the ring roller itself and minimizevibrations of this ring roller being transmitted to the casing side,thereby achieving further noise reduction.

[0124] This type of method for fixing the ring roller is highlyadvantageous in terms of noise suppression, as described previously. Inaddition to this simple noise reduction, the method also eliminates theneed for the process of press-fitting the ring roller, thereby improvingthe assembling efficiency.

[0125] Here, the ring roller may be configured to be adjustable in axisposition within the mounting reference surface. In such a configuration,the axis of the ring roller can be readily adjusted to coincide with theaxes of the respective power transmission shafts of the oscillatinginternal meshing planetary gear unit and external unit to which thefrictional transmission unit is coupled. This allows quicker, easierassembly of the frictional transmission unit. More specifically, whenthe ring roller was mounted by press-fit, the axis adjustment(alignment) was impossible unless the oscillating internal meshingplanetary gear unit and the external unit were displaced. On the otherhand, when the ring roller is free from radial pressures and is providedwith enough spaces for radial displacement as in the present invention,the axis is easy to adjust, and therefore assembling efficiency isimproved dramatically.

[0126] Moreover, in order to draw the best out of the coaxiality whichis the merit of the present invention, the sun roller may be providedwith a sun-roller-side shaft insertion hole into which a powertransmission shaft of the external unit is insertable, and the planetarycarrier is provided with a carrier-side shaft insertion hole into whicha power transmission shaft of the oscillating internal meshing planetarygear unit is insertable, so as to form the frictional transmission unitinto a shaft coupling structure for allowing relative rotations of thepower transmission shafts.

[0127] Such constitution is highly advantageous in the following aspect.That is, the coaxiality between the input and output elements of thesimple planetary roller mechanism makes the present invention easilyapplicable to a geared motor that has a now-commonly-known structure inwhich the drive shaft of the external unit and the input and outputshafts of the oscillating internal meshing planetary gear unit arealigned on a single center axis and these units are coupled with eachother by an ordinary coupling.

[0128] For example, in the conventional geared motor 1 as shown in FIG.22, the motor shaft 61 of the motor unit 3 and the first shaft 11 of theoscillating internal meshing planetary gear unit 2 are coupled with eachother by a common coupling (shaft coupling). Geared motors of suchstructure are not limited to that shown in FIG. 22. Most of theconventional driving apparatuses containing an oscillating internalmeshing planetary gear unit and an external unit have similarstructures. Under such circumstances, the frictional transmission unitprovided with the “shaft coupling structure” by forming shaft insertionholes in the carrier and sun roller can be employed and replaced withthe ordinary coupling to easily realize the driving apparatus of thepresent invention with only slight changes in design. Moreover, thesimple planetary roller mechanism can be realized into an axiallycompact configuration, causing no axial extension of the entire drivingapparatus.

[0129] In particular, the application of the “shaft coupling structure”to a frictional transmission unit is combined with the adoption of amounting reference surface to allow the frictional transmission unit tobe replaced by another frictional transmission unit of differentreduction ratio, with almost the same trouble as that required inreplacing ordinary couplings. Therefore, it becomes possible to flexiblyadapt this driving apparatus to user demands for a wide range ofreduction ratios. Here, what needs to be replaced is the frictionaltransmission unit alone; therefore, the replacement costs less ascompared to the replacement of the entire geared motor.

[0130] In the frictional transmission unit of “shaft couplingstructure,” at least either the sun-roller-side shaft insertion hole orthe carrier-side shaft insertion hole is formed into a floatingconnection structure with respect to the power transmission shaftinserted therethrough. This realizes the aforementioned floatingconnection structure on the shaft coupling portion of the frictionaltransmission unit with the oscillating internal meshing planetary gearunit or the external unit.

[0131] In particular, the ring roller of this frictional transmissionunit is fixed to the casing on the basis of the mounting referencesurface. Therefore, unlike ordinary couplings which are simply fittedonto shafts to keep their own positions (by being supported by theshafts in return), such as those shown in FIGS. 22 and 23, thisfrictional transmission unit can keep its own position independent ofthe power transmission shafts. As a result, each power transmissionshaft and the corresponding shaft insertion hole can maintain a constantclearance therebetween all the time, further ensuring the blockage ofvibrations and noises. Given that this frictional transmission unit isadjustable in axis, the clearances can also be set precisely from thebeginning. This combines with the maintenance of constant clearances toachieve further suppression of noises and vibrations.

[0132] In a concrete method for fixing the ring roller to the casing,the ring roller is provided with a bolt hole piercing therethrough inthe direction of the rotation axis so that the ring roller is fixable tothe mounting reference surface by a fixing bolt inserted through thebolt hole and threadedly engaged with a tapped hole formed in themounting reference surface. Here, the bolt hole has a diameter somewhatgreater than that of the fixing bolt so that the ring roller isadjustable in axis position within the mounting reference surface aslong as the fixing bolt is fitted to the bolt hole with play.

[0133] This allows the ring roller to be surely fixed by the most commonmeans, or bolts, with no particular increase in manufacturing costs.Besides, since the axis position of the ring roller can be adjusted bythe simpler method, suppression in cost is possible and the assembly isfacilitated.

[0134] Furthermore, the planetary carrier of the simple planetary rollermechanism may be provided with pins which penetrate through center holesformed at the rotational centers of the respective planetary rollers toretain the planetary rollers at constant mutual positions. Then, aninner roller of generally cylindrical shape is inserted to the clearancebetween the outer peripheral surface of each pin and the innerperipheral surface of the corresponding center hole so that the innerroller makes sliding rotation with respect to both the peripheralsurfaces.

[0135] In such constitution, the inner rollers can make rotations whilesliding over the outer peripheral surfaces of the pins and the innerperipheral surfaces of the planetary rollers, to absorb the differencein rotational speed between the pins and the planetary rollers. Morespecifically, the inner rollers inserted to between the pins and theplanetary rollers make rotations at a speed intermediate between therevolving speed of the pins and the rotating speed of the planetaryrollers. Therefore, as compared to the case where the pins and theplanetary rollers are in “direct” contact with each other, the inner andouter contact surfaces of the inner rollers slide at a speeddifferential smaller than the actual difference in rotational speedbetween the pins and the planetary rollers. This consequently allowsreductions of frictional heat generation, frictional resistance, and thelike. The inner rollers also offer superior strength as compared toneedle rollers, thereby enhancing the durability in long run andhigh-speed rotations.

[0136] The present invention has been described so far in terms ofinter-unit coupling. As described below, another aspect of the presentinvention consists in a driving apparatus separated from external units.

[0137] That is, the present invention may also be regarded as comprises:a rotating shaft (214, 414 in the embodiment) to be connected to anexternal unit; an oscillating internal meshing planetary gear mechanismhaving an internal gear and an external gear making internal contactwith the internal gear, the center of the internal gear lying inside theperiphery of the external gear; and a frictional transmission unit ofsimple planetary roller mechanism, having friction rollers consisting ofa sun roller, a plurality of planetary rollers being retained by aplanetary carrier and making rolling contact with the outer periphery ofthe sun roller, and a ring roller having the planetary rollers arrangedinside so as to make internal contact. Here, one of the sun roller,planetary carrier, and ring roller is fixed. Either of the other two iscoupled to the oscillating internal meshing planetary gear mechanism.The remaining one is coupled to the rotating shaft.

[0138] Again, it is preferable that: the ring roller is fixed, theplanetary carrier is coupled to the oscillating internal meshingplanetary gear mechanism, and the sun roller is coupled to the rotatingshaft. Of the coupling portions between the planetary carrier and theoscillating internal meshing planetary gear mechanism and between thesun roller and the rotating shaft, at least one coupling portionpreferably has a floating connection structure.

[0139] For the above-mentioned oscillating internal meshing planetarygear mechanism, an oscillating internal meshing planetary gear mechanismmay be adopted which has a first shaft and a second shaft located on thecenter axis of the driving apparatus. Here, an external gear is fittedon the outer periphery of the first shaft via an eccentric body so as tobe capable of oscillating rotations with respect to the first shaft. Aninternal gear with which the external gear meshes internally is providedconcentrically with the first shaft. The second shaft is coupled to theexternal gear via means for extracting only the rotational component ofthe external gear.

[0140] Incidentally, focusing attention on the combination of “africtionally-engaging unit and a floating connection” can also result ina frictional transmission unit 2300 as shown in FIG. 21, for example. Inthe diagram, the reference numeral 2301 represents the input-side shaftto be connected to a motor shaft 2161 via a floating connection portionF1, the numeral 2302 an input-side roller arranged on the shaft 2301,the numeral 2303 the output-side shaft to be connect to a first shaft2111 of a reduction gear unit 2102 via a floating connection portion F2,and the numeral 2304 an output-side roller arranged on the shaft 2303.The reference numeral 2305 represents the idle shaft arranged inparallel to the aforementioned input- and output-side shafts 2301 and2303. On this shaft 2305 are arranged first idle roller 2306 and secondidle roller 2307 coming into contact with the aforementioned input- andoutput-side rollers 2302 and 2304, respectively.

[0141] This frictional transmission unit 2300 transmits rotations of themotor shaft 2161 in such order that: floating connection portionF1→input-side shaft 2301→input-side roller 2302→first idle roller2306→idle shaft 2305→second idle roller 2307→output-side roller2304→output-side shaft 2303→floating connection portion F2→first shaft2111.

[0142] At first glance, the frictional transmission unit 2300 and thefloating connections in combination appear to offer a noise reductioneffect. And this configuration indeed produced some effect. However, thenoise reducing effect produced was not as “dramatic” as that of thepresent invention.

[0143] Now, the following is one of the constitutions effective for themost rational realization of the present invention.

[0144] That is, a driving apparatus comprising a drive unit forgenerating rotational power, a first reduction mechanism unit coupled toan output shaft of the drive unit to transmit the rotational power, anda second reduction mechanism unit of support carrier transmission type,including reduction gears to be coupled to the first reduction mechanismunit, and a pair of support carriers rotatably supported by a casing atboth axial outsides of the reduction gears via bearings, the supportcarriers for extracting rotational power of the reduction gears,wherein: the above-mentioned first reduction mechanism unit has a simpleplanetary roller structure of friction transmission type, including asun roller to be coupled to a drive shaft of the drive unit, a planetaryroller making rolling contact with the outer periphery of the sunroller, a ring roller with which the planetary roller makes internalcontact, and a planetary carrier for extracting the revolution componentof the planetary roller and transmitting the same to an input shaft ofthe second reduction mechanism unit, the outside diameter of the ringroller being set within the outside diameter of the bearing supportingthe drive-unit-side support carrier of the pair of support carriers inthe second reduction mechanism unit; and the above-described ring rolleris situate within the casing, in a space on the drive-unit side of thebearing.

[0145] In short, the first reduction mechanism unit serving as thepreceding reduction side of the driving apparatus is constituted as asimple planetary roller mechanism of frictional transmission type, andthe outside diameter of the ring roller in the first reduction mechanismunit is set within the outside diameter of the bearing in the secondreduction mechanism unit. This makes it possible to couple the first andsecond reduction mechanism units to each other with a highly compactconfiguration.

[0146] When this constitution is adopted, the space within the casing,on the drive-unit side of the bearing can be so expanded as toaccommodate the simple planetary roller mechanism, with only anextremely simple change in design (namely, just a little extension ofthe casing). Moreover, this expanded space has little effect on the sizeof the entire driving apparatus.

[0147] Setting the outside diameter of the ring roller within that ofthe above-mentioned bearing makes the ring roller mountable to thecasing from the side opposite to the drive unit (with the bearingdetached), i.e., from the side closer to the second reduction mechanismunit to be mounted later. This greatly simplifies the internalconfiguration of the casing, and significantly facilitates themanufacture and assembly of the apparatus (the manufacturing and othermethods will be described later).

[0148] Accordingly, it becomes possible to arrange the first reductionmechanism unit of simple planetary roller mechanism into the space onthe drive-unit side of the bearing, within the same casing as thatcontaining the second reduction mechanism unit. Therefore, the first andsecond reduction mechanism units can be combined with each other toachieve reduction ratios high enough to meet the market needs whilegreatly decreasing the axial dimension and reducing the manufacturingcosts as compared to the conventional ones. Obviously, the drivingapparatus constituted as described above can output the power of thedrive unit without losing the coaxiality. The driving apparatusundergoes no increase in radial dimension.

[0149] Furthermore, this driving apparatus can realize the inherent,as-provided effects of the present invention. That is, the firstreduction mechanism unit, because of being a frictional transmissiontype, is capable of quiet operation. In addition, both the first andsecond reduction mechanism units can be accommodated in a single casing.Therefore, the resonance and other phenomena conventionally caused bythe internal spaces of two casings can be suppressed. Moreover, sincethe vibration transmission between the drive unit (motor) and the secondreduction mechanism unit is blocked due to the presence of the firstreduction mechanism unit of frictional transmission type, the resonancein the respective units is lowered and operational noises are reduced.The result is that the three requirements having been regarded asdifficult to meet, i.e., a high reduction ratio, a compactconfiguration, and quietness, can be satisfied rationally.

[0150] Constituting the driving apparatus as described above alsoachieves a considerable simplification of the manufacturing steps. Theconcrete manufacturing method comprises the steps of: mounting the driveunit on the casing; attaching the first reduction mechanism unit to thiscasing with the drive unit mounted thereon, from the side opposite tothe drive unit; and attaching the second reduction mechanism unit to thecasing with the first reduction mechanism unit attached thereto.

[0151] This manufacturing method is highly labor-saving because thefirst and second reduction mechanism units (coaxial with each other) canbe sequentially built in with reference to the drive shaft of the driveunit which has been fixed to the casing initially.

[0152] In particular, the simple planetary roller structure adopted forthe first reduction mechanism unit and the oscillating internal meshingplanetary gear structure adopted for the second reduction mechanismunit, both are high in modularity. Therefore, these units can beindependently assembled to some extent before built into the casingtogether. Moreover, both the structures are intended for coaxialtransmission of the rotational power, they facilitate the positioningand permit quick assembly.

[0153] In terms of the assembly facilitation, it is preferable that boththe coupling structures between the output shaft of the drive unit andthe sun roller of the first reduction mechanism unit and between theplanetary carrier of the first reduction mechanism unit and the firstshaft of the second reduction mechanism unit have a spline connectionstructure for allowing axial play. By this means, the first and secondreduction mechanism units hardly require fine-adjustment in theirmounting steps, and thus can be assembled still more easily and quickly.

[0154] The second reduction mechanism unit of this driving apparatusessentially has a support carrier transmission type structure, whichincludes a speed reducer to be coupled to the first reduction mechanismunit, and a pair of support carriers rotatably supported by the casingat both axial outsides of the speed reducer via bearings to extract therotational power of the speed reducer. As a matter of course, even anoscillating internal meshing planetary gear structure of support carriertransmission type is similarly applicable to the second reductionmechanism unit. This constitution may also be combined with theabove-described constitution for the “mounting reference surface.”

[0155] The nature, principle, and utility of the invention will becomemore apparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts aredesignated by like reference numerals or characters.

BRIEF DESCRIPTION OF THE DRAWINGS

[0156] In the accompanying drawings:

[0157]FIG. 1 is a sectional view of a geared motor shown as anembodiment of the present invention;

[0158]FIG. 2 is a sectional view of the frictional transmission unit(the simple planetary roller mechanism) in the geared motor;

[0159]FIG. 3 is a view taken along the arrowed line III-III of FIG. 2;

[0160]FIG. 4 is a sectional view taken along the allowed line IV-IV ofFIG. 1;

[0161]FIG. 5 is a view similar to FIG. 4, showing a configuration foranother reduction ratio;

[0162]FIG. 6 is a sectional view of a geared motor shown as anotherembodiment of the present invention;

[0163]FIG. 7 is a sectional view of the frictional transmission unit(the simple planetary roller mechanism) in the geared motor;

[0164]FIG. 8 is a view taken along the arrowed line VIII-VIII of FIG. 7;

[0165]FIG. 9 is a chart listing the types of geared motors prepared assamples for noise measurement;

[0166]FIG. 10 is a table showing the noise measurements;

[0167]FIG. 11 is a graph showing the noise measurements;

[0168] FIGS. 12(a) through 12(f) are charts showing noise spectra bytype;

[0169] FIGS. 13(a) through 13(f) are charts showing noise spectra bytype;

[0170] FIGS. 14(a) through 14(f) are charts showing noise spectra bytype;

[0171] FIGS. 15(a) through 15(f) are charts showing noise spectra bytype;

[0172]FIG. 16 is a chart listing the input-output-fixed combinationsselectable for a simple planetary roller apparatus;

[0173] FIGS. 17(A) to 17(C) are schematic diagrams showing theassembling processes of the driving apparatus;

[0174]FIG. 18 is a sectional view of a geared motor shown as anotherembodiment of the present invention;

[0175]FIG. 19 is a sectional view of the frictional transmission unit(the simple planetary roller mechanism) in the geared motor;

[0176]FIG. 20 is a view taken along the arrowed line XX-XX of FIG. 19;

[0177]FIG. 21 is a schematic perspective view showing another example ofthe frictional transmission unit;

[0178]FIG. 22 is a sectional view of a conventional geared motor;

[0179]FIG. 23 is a sectional view of a conventional,power-distributed-shaft-typed oscillating internal meshing planetarygear structure;

[0180]FIG. 24 is a schematic sectional view taken along the arrowed lineXXIV-XXIV of FIG. 23;

[0181]FIG. 25 is a sectional view of a geared motor for use in the noisemeasurement as a comparative example;

[0182]FIG. 26 is a sectional view of another geared motor for use in thenoise measurement as a comparative example;

[0183]FIG. 27 is a sectional view of yet another geared motor for use inthe noise measurement as a comparative example; and

[0184]FIG. 28 is a sectional view of a conventional driving apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0185] Hereinafter, preferred embodiments of the present invention willbe described with reference to the accompanying drawings.

[0186]FIG. 1 is a sectional view of the geared motor shown as anembodiment, and FIG. 2 is an enlarged sectional view of the frictionaltransmission unit (the frictional transmission mechanism) therein. FIG.3 is a view taken along the arrowed line III-III of FIG. 2, and FIG. 4is a view taken along the arrowed line IV-IV of FIG. 1. FIG. 5 is a viewsimilar to FIG. 4, showing an example for another reduction ratio.

[0187] Incidentally, in the following descriptions, like or similarparts to those of the conventionally known arrangement shown in FIG. 18will be designated by like reference numerals having the same lower twodigits, and obviously repetitive descriptions thereto will be omitted.

[0188] This geared motor 101 has a reduction gear unit (the oscillatinginternal meshing planetary gear unit, the oscillating internal meshingplanetary gear mechanism, and the second reduction mechanism unitdescribed above) 102 and a motor unit (the external unit, the driveunit) 103 connected and integrated with each other. The reduction gearunit 102 contains an oscillating internal meshing planetary gearstructure. A frictional transmission unit (the frictional transmissionmechanism, the first reduction mechanism unit) 104 is interposed betweenthe reduction gear unit 102 and the motor unit 103. This frictionaltransmission unit 104 comprises a single planetary roller mechanism 202for transmitting rotational power between the units 102 and 103 by meansof the friction among a plurality of rollers (the friction rollers)contacting one another.

[0189] The reduction gear unit 102 has a casing 151 which is composed ofa central casing 152 disposed at the axial center, a joint casing 153 onthe side closer to the motor unit 103, and a front casing 154 on theside opposite from the motor unit 103. The motor unit 103 has a casing155 which is composed of a cylindrical casing 156 having a stator formedinside, the joint casing 153 on the side closer to the reduction gearunit 102, and a rear cover 157 on the side opposite from the reductiongear unit 102.

[0190] Here, the joint casing 153 comprises both parts of the casings151 and 155 of the reduction gear unit 2 and the motor unit 3. Throughthe intervention of this joint casing 153, the reduction gear unit 102and the motor unit 103 are integrally connected with each other. Then,the simple planetary roller mechanism 202 serving as the frictionaltransmission unit 104 is arranged inside the joint casing 153.

[0191] Here, the simple planetary roller mechanism 202 corresponds tothe preceding-stage reduction part. The oscillating internal meshingplanetary gear structure serving as the reduction gear unit 102corresponds to the subsequent-stage reduction part.

[0192] The reduction gear unit 102 has a first shaft 111 serving as theinput shaft (the high-speed shaft) and a second shaft 112 serving as theoutput shaft (the low-speed shaft) both on the center axis L of theunit.

[0193] Two eccentric bodies 113 a and 113 b are fitted on the outerperiphery of the first shaft 111 so as to axially adjoin each other witha given phase difference therebetween (180°, in this embodiment). Theseeccentric bodies 113 a and 113 b make rotations together with the firstshaft 111. As shown in FIG. 4, the respective centers O1 of theeccentric bodies 113 a and 113 b are off the center O2 of the firstshaft 111 with a given eccentricity e. External gears 115 a and 115 bare fitted on the outer peripheries of the eccentric bodies 113 a and113 b via bearings 114 a and 114 b, respectively.

[0194] The plural rows of external gears 115 a and 115 b fitted onto theeccentric bodies 113 a and 113 b have a plurality of inner pin holes 116a and 116 b, respectively. Inner pins 117 are fitted into these innerpin holes 116 a and 116 b with some play.

[0195] On the outer peripheries of the external gears 115 a and 115 bare provided outward teeth each having a trochoidal tooth profile or acircular arc tooth profile. These outward teeth come into internal meshwith an internal gear 120 which is provided concentrically with thefirst shaft 111. The internal gear 120 is integrally formed on the innerperiphery of the central casing 152. Each inward tooth of the internalgear 120 is formed with an outer pin 121 retained on the inner peripheryof the central casing 152.

[0196] The difference in the number of teeth between each external gear115 a, 115 b and the internal gear 120 is “4” in the example of FIG. 4,and “1” in the example of FIG. 5.

[0197] The two external gears 115 a and 115 b are interposed between apair of support carriers (the support carriers) 123 and 124. The supportcarriers 123 and 124 are rotatably supported by bearings 131 and 132fitted to the inner peripheries of the joint casing 153 and the frontcasing 154, respectively. The support carriers 123 and 124 are alsointegrally connected with each other by a plurality of carrier pins(coupling pins) 125 and spacers 126 piercing through the external gears115 a and 115 b.

[0198] The inner pins 117, fitted to the inner pin holes 116 a and 116 bin the external gears 115 a and 115 b with some play, are supported atboth ends by the pair of carriers 123 and 124 on both sides so as to becapable of sliding rotations. This allows only the rotational componentsof the external gears 115 a and 115 b to be transmitted to the carriers123 and 124 through the inner pins 117.

[0199] The support carrier 123 closer to the motor unit 103 is ofannular shape having a center hole 123 a. One end (a spline shaftportion, to be described later) 111 a of the first shaft 111 lies insidethe center hole 123 a.

[0200] The other carrier 124 is integrally formed on the base of thesecond shaft 112, and provided with a recess 124 a into which the otherend 111 b of the first shaft 111 is inserted. The first shaft 111 isrotatably supported by bearings 133 and 134. The bearing 133 is fittedto the inner periphery of the through hole 123 a in the carrier 123, andthe bearing 134 is fitted to the inner periphery of the other carrier124.

[0201] The motor shaft (the drive shaft, the rotating shaft) 161 of themotor unit 103 is supported at its rear end by a bearing 162 and at itsfront end by a bearing 163. The bearings 162 and 163 are fitted to therear cover 157 and the joint casing 153, respectively. The motor shaft161 is arranged to be coaxial with the center axis L of the reductiongear unit 102.

[0202] The geared motor 101 so far has almost the same constitution asthat of the conventional geared motor 1 of FIG. 22.

[0203] A difference consists in that a new space is secured next to thebearing 131 supporting the support carrier 123 closer to the motor unit103, and the simple planetary roller mechanism 202 is built into thespace as the above-mentioned frictional transmission unit 104.

[0204] To contain this simple planetary roller mechanism 202, the jointcasing 153 is somewhat extended in axial dimension. The joint casing 153also has a deeply-bored recess portion 251 formed in its inner peripheryfrom the side closer to the reduction gear unit 102. The simpleplanetary roller mechanism 202 is mounted on the bottom, or the sidecloser to the motor unit 103, of the recess portion 251.

[0205] As shown in FIGS. 2 and 3, the simple planetary roller mechanism202 has the friction rollers consisting of a sun roller 211, a plurality(four, in this embodiment) of planetary rollers 212, and a ring roller213. The sun roller 211 has a spline shaft portion 214. The planetaryrollers 212 are of hollow cylindrical shape, and make rolling contactwith the outer periphery of the sun roller 211. The ring roller 213 hasan inside diameter D3 somewhat smaller than the sum of the diameter D1of the sun roller 211 and the value twice the diameter D2 of theabove-mentioned planetary rollers 212. The ring roller 213 has theplanetary rollers 212 arranged inside so as to make internal contact.

[0206] In this case, the ring roller 213 is fixed to the joint casing153 by through bolts 252 to make the fixed element of the simpleplanetary roller mechanism 202. The sun roller 211 makes the inputelement, and a planetary carrier 215 supporting the planetary rollers212 makes the output element.

[0207] The planetary carrier 215 for extracting the revolutions of theplanetary rollers 212 has an output shaft portion 216 of hollowcylindrical shape, projected toward the reduction gear unit 102, and aretainer portion (the retainer) 217 of generally annular shape. An innerspline 218 is formed in the inner periphery of the output shaft portion216.

[0208] Four circular recesses 219 each having an open end on the sideopposite from the output shaft portion 216 are formed in the retainerportion 217 of the planetary carrier 215 at regular intervals along thecircumferential direction. Each of the recesses 219 accommodates one ofthe planetary rollers 212 rotatably. Each of the circular recesses 219has a peripheral surface that is partially open to both the outer andinner sides of the retainer portion 217. Each of the planetary rollers212 exposes a part of its peripheral surface from the outer-side opening219 a to make contact with the inner periphery of the ring roller 213.Each of the planetary rollers 212 also exposes a part of its peripheralsurface from the inner-side opening 219 b to make contact with the outerperiphery of the sun roller 211.

[0209] This retainer portion 217 occupies the spaces around theplurality of planetary rollers 212 to retain the planetary rollers 212at constant mutual positions. Thus, the planetary carrier 215 providedwith this retainer portion 217 functions to rotatably retain theplanetary rollers 212 and to extract the revolution components of theplanetary rollers 212.

[0210] Arranged on both end faces of the ring roller 213 are side plates221 of annular shape. By these side plates, the contact surface of thering roller 213 with the planetary rollers 212 is shielded from outsideall over the circumference. This shielded space is also sealed frominside by the outer peripheries of the retailer portion 217 so thattraction grease priced higher than gear grease is enclosed in theshielded space. The role of the traction grease is to ensure frictionalforces, not to reduce friction.

[0211] In addition, a partition plate 222 is arranged at the end of thesun roller 211 to separate the space accommodating the sun roller 211from the internal space of the output shaft portion 216.

[0212] This simple planetary roller mechanism 202 is assembled, forexample, in a manner as follows:

[0213] Initially, the planetary rollers 212 are mounted on the retainerportion 217 of the planetary carrier 215. Then, the planetary rollers212 as-mounted are put into external contact with the outer periphery ofthe sun roller 211. In that state, the ring roller 213 is heated toexpand, and the planetary rollers 212 retained by the planetary carrier215 are inserted into the bore of the ring roller 213. This subsequentlycools to complete the simple planetary roller mechanism 202 in which thering roller 213 and the planetary rollers 212, as well as the planetaryrollers 212 and the sun roller 211, are in contact with each other at agiven contact pressure.

[0214] The simple planetary roller mechanism 202 as-preassembled is thenaccommodated into the bottom of the recess portion 251 formed in thejoint casing 153, with the output shaft portion 215 of the planetarycarrier 215 directed toward the reduction gear unit 102 and the splineshaft portion 214 of the sun roller 211 directed toward the motor unit103. Then, the through bolts 252 inserted through the ring roller 213are screwed into the bottom wall of the recess portion 251 to fix thesimple planetary roller mechanism 202 to the joint casing 153.Incidentally, this point will be detailed later.

[0215] In this state, the output shaft portion 216 on the planetarycarrier 215 of the simple planetary roller mechanism 202 is insertedinto the center hole 123 a which is formed in the support carrier 123closer to the motor unit 103, of the reduction gear unit 102.

[0216] The bearing 131 supporting the support carrier 123 of thereduction gear unit 102 is fitted to the mouth of the recess portion251. This bearing 131 is axially positioned by a spacer 253 lyingbetween the bearing 131 and the simple planetary roller mechanism 202.

[0217] Thus, the simple planetary roller mechanism 202 is interposedbetween the reduction gear unit 102 and the motor unit 103. The sunroller 211 of the simple planetary roller mechanism 202 and the motorshaft 161 of the motor unit 103 are connected with each other via acoupling 170. The output shaft portion 216 on the planetary carrier 215of the simple planetary roller mechanism 202 and the first shaft 111 ofthe reduction gear unit 102 are coupled with each other by inserting theextremity (spline shaft portion) 111 a of the first shaft 111 into thebore of the output shaft portion 216.

[0218] Here, through the intervention of the coupling 170 equipped withan inner spline 170 a, a spline shaft portion 161 a on the extremity ofthe motor shaft 161 and the spline shaft portion 214 of the sun roller211 come into floating connection with each other while allowing radialplay therebetween. In addition, the spline shaft portion 111 a on theextremity of the first shaft 111 is inserted to the output shaft portion216 equipped with the inner spline 218, so that the output shaft portion216 of the planetary carrier 215 and the first shaft 111 come intofloating connection with each other while allowing radial playtherebetween.

[0219] Due to the partition plate 222 arranged inside the planetarycarrier 215 of the simple planetary roller mechanism 202, the internalspace of the output shaft portion 216 is sealed off at the contact areawith the end face of the sun roller 211. This allows the simpleplanetary roller mechanism 202 to be filled with grease that iseffective for frictional transmission, in distinction from thelubricating oil for the reduction gear unit 102.

[0220] Next, description will be given of the operation of the gearedmotor 101.

[0221] When the motor shaft 161 is rotated, the rotation is transmittedto the sun roller 211 of the simple planetary roller mechanism 202 tourge the rotation of the planetary rollers 212. Here, the planetaryrollers 212 are in contact with the fixed ring roller 213. Therefore,the planetary rollers 212 make rotations and revolutions along the innerperiphery of the ring roller 213, and the revolution components areinput to the first shaft 111 of the reduction gear unit 102 via theplanetary carrier 215.

[0222] Then, as in the conventional examples, the external gears 115 aand 115 b make oscillations while making internal contact with theinternal gear 120. As a result, the rotational components in theoscillations of the external gears 115 a and 115 b are extracted to thesecond shaft 112 via the support carriers 123 and 124.

[0223] During the power transmission described above, the reduction gearunit 102 and the motor unit 103 independently produce specificvibrations. However, the coupling portions of the reduction gear unit102 with the units 102 and 103 on both sides, namely, the couplingportion between the planetary carrier 215 and the first shaft 111 andthe coupling portion between the sun roller 211 and the motor shaft 161are provided with the spline mechanisms (the floating connectionstructures) for allowing radial play. These portions first absorbvibrations (radial vibrations, especially) participating thetransmission between the reduction gear unit 102 and the motor unit 103on both sides.

[0224] Between the units 102 and 103 are interposed the simple planetaryroller mechanism 202 as the frictional transmission unit 104. Therefore,those vibrations (circumferential vibrations and axial vibrations,especially) participating the transmission between the reduction gearunit 102 and the motor unit 103 on both sides are then absorbed by thecontact surfaces within the simple planetary roller mechanism 202,namely, the contact surfaces between the sun roller 211 and theplanetary rollers 212, the contact surfaces between the planetaryrollers 212 and the ring roller 213, and even the contact surfacesbetween the planetary rollers 212 and the planetary carrier 215. Thisensures the interception of the vibration transmission between the units102 and 103 on both sides.

[0225] As a result, the complex resonance phenomena resulting from thevibration transmission between the reduction gear unit 102 and the motorunit 103 are avoided to reduce the levels of the vibrations and noisesproduced by the entire geared motor 101.

[0226] In other words, the simple planetary roller mechanism 202 (104)is deliberately interposed between the reduction gear unit 102 and themotor unit 103 as a third unit. Due to this, the vibration transmissionfrom the reduction gear unit 102 to the motor unit 103 and the vibrationtransmission from the motor unit 103 to the reduction gear unit 102 canbe effectively suppressed to reduce the vibrations and noises of theentire geared motor 101 consequently.

[0227] The reduction of vibration gives greater durability to thecomponent parts of the motor unit 103, as well as the component parts ofthe reduction gear unit 102 such as the external gears 115 a, 115 b, theeccentric bodies 113 a, 113 b, and the internal gear 120.

[0228] As described previously, the shaft coupling portions of thesimple planetary roller mechanism 202 (104) with the reduction gear unit102 and the motor unit 103 on both sides are provided with the floatingconnection structures for allowing radial play. This makes it possibleto prevent the planetary rollers 212 and the sun roller 211 beingsubjected to radial external forces (and vibrations) from the units 102and 103 on both sides.

[0229] Accordingly, fluctuations in contact pressure at the contactsurfaces between the planetary rollers 212 and the sun roller 211 and atthe contact surfaces between the planetary rollers 212 and the ringroller 213 can be suppressed. This in turn suppresses torquetransmission fluctuations in the simple planetary roller mechanism 202,thereby allowing stable, sure torque transmission.

[0230] The reduction gear unit 102 used in this geared motor 101 hasboth the first and second shafts 111 and 112 aligned on its center axisL. Therefore, this reduction gear unit 102 of its simple, compactstructure has a merit that its rigidity can be increased to realizehigher torque transmission by that much.

[0231] For example, the first shaft 111, which undergoes the maximuminfluence from the loads of the external gears 115 a and 115 b, can beset at higher rigidity to ease the problem of flexure-originatedvibrations.

[0232] Now, unlike the conventional power-distributed shaft typetechnology described above, the planetary rollers 212 are supported bythe planetary carrier 215 which is isolated from thevibration-generating first shaft 111. Accordingly, even in the caseswhere vibrations or deformations arise on the first shaft 111, theirinfluences are kept from reaching the roller contact surfaces of thesimple planetary roller mechanism 202. Thus, the simple planetary rollermechanism 202 can also realize sure, stable torque transmission throughthese contact surfaces.

[0233] In the geared motor 101 described above, the newly-added simpleplanetary roller mechanism 202 is built into the joint casing 153 forconnecting the reduction gear unit 102 and the motor unit 103. Thisallows the improvement to be made without a great change in thestructures of the reduction gear unit 102 and the motor unit 103 on bothsides.

[0234] In particular, the simple planetary roller mechanism 202 has bothits input part (the sun roller 211) and output part (the output shaftportion 216 of the planetary carrier 215) on the same axis. Hence, thegeared motor 101 of this embodiment can be produced with only a slightchange to the conventional geared motor 1 of FIG. 22. This point willalso be detailed later.

[0235] The simple planetary roller mechanism 202 is capable of speedreduction by itself. Therefore, the geared motor 101 which combine thesimple planetary roller mechanism 202 at the preceding stage and thereduction gear unit 102 of oscillating internal meshing planetary gearstructure type at the subsequent stage can achieve higher totalreduction ratios. Moreover, unlike gears, the simple planetary rollermechanism 202 is easy to set the reduction ratio finely. This allowseasy provision of a series of geared motors with many steps of reductionratios, or a geared motor having a particular reduction ratiocorresponding to a specific application.

[0236] For example, it is possible to prepare a number of reduction gearunits 102 of oscillating internal meshing planetary gear structure typefor geometrically progressive reduction ratios. These reduction gearunits 102 can be combined with the first-stage reduction of the simpleplanetary roller mechanism 202 to realize geometrically-progressivetotal reduction ratios in a number of steps.

[0237] The preceding-stage torque transmission by means of thefrictional transmission can ensure only a small amount of transmissiontorque. This, however, does not matter for the reasons that the amountof torque to transmit at the preceding-stage reduction is rather smallin the first place, and that the preceding stage realizes stablerotations as blocked from vibrations.

[0238] The embodiment described above has dealt with the case where thefrictional transmission unit 104 is interposed between the reductiongear unit, or the oscillating internal meshing planetary gear unit, 102and the motor unit 103. However, the frictional transmission unit canalso be interposed between the oscillating internal meshing planetarygear unit and any other external unit to promise the sameresonance-preventing effect as that mentioned above.

[0239] For example, in the case where the second shaft 112 and anexternal unit coupled thereto may produce resonance, a frictionaltransmission unit is recommended to be interposed between the secondshaft and the input shaft of the external unit.

[0240] When the oscillating internal meshing planetary gear unit is usedas step-up gears, its second shaft makes the input shaft, and its firstshaft the output shaft; therefore, the second shaft is connected to themotor unit, and the first shaft is to the external unit. Even in thiscase, the frictional transmission unit is appropriately interposedbetween units that may produce resonance.

[0241] The embodiment described above has also dealt with the case wherethe planetary carrier 215 for retaining the planetary rollers 212 isprovided with the retainer portion 217, and this retainer portion 217retains the plurality of planetary rollers 212 at constant mutualpositions. However, the frictional transmission unit may employ a simpleplanetary roller mechanism that retains the planetary rollers by meansof pins.

[0242]FIG. 6 shows a geared motor 301 which adopts a pin-typed simpleplanetary roller mechanism 402 for its frictional transmission unit 304.FIG. 7 is an enlarged sectional view of the simple planetary rollermechanism 402, and FIG. 8 is a view taken along the arrowed lineVIII-VIII of FIG. 7. Incidentally, this geared motor 301 has almost thesame constitution as that of the geared motor 101 shown in FIGS. 1-5,with only the slight difference in the type of the simple planetaryroller mechanism 402 from that of FIGS. 1-5. Accordingly, in thefollowing descriptions, like parts to those shown in FIGS. 1-5 will bedesignated by reference numerals having the same lower two digits, andrepetitive descriptions thereto will be omitted. Here, thoseone-hundreds numerals in FIGS. 1-5 will be represented inthree-hundreds, and those two-hundreds in four-hundreds.

[0243] As shown in FIGS. 7 and 8, the simple planetary roller mechanism402 of this geared motor 301 has friction rollers consisting of a sunroller 411, a plurality (four, in this embodiment) of planetary rollers412, and a ring roller 413. The sun roller 411 has a spline shaftportion 414. The planetary rollers 412 are of hollow cylindrical shape,and make rolling contact with the outer periphery of the sun roller 411.The ring roller 413 has an inside diameter D3 somewhat smaller than thesum of the diameter D1 of the sun roller 411 and the value twice thediameter D2 of the above-mentioned planetary rollers 412. The ringroller 413 has the planetary rollers 412 arranged inside so as to makeinternal contact.

[0244] As shown in FIG. 6, the ring roller 413 is again fixed to thejoint casing 353 by through bolts 452, making the fixed element of thesimple planetary roller mechanism 402. The sun roller 411 makes theinput element, and a planetary carrier 415 supporting the planetaryrollers 412 makes the output element.

[0245] The planetary carrier 415 for extracting the revolutions of theplanetary rollers 412 has an output shaft portion 416 of hollowcylindrical shape, projected toward the reduction gear unit 302 from anannular flange portion 415 a. The planetary carrier 415 is also providedwith four pins 417 which are fitted and fixed to the flange portion 415a at their bases and projected toward the motor unit 303 at theirextremities. An inner spline 418 is formed in the inner periphery of theoutput shaft portion 416.

[0246] The respective planetary rollers 412 are rotatably fitted on theouter peripheries of the pins 417 via needle bearings 419 so that theplanetary rollers 412 are retained at constant mutual positions. In thatstate, the respective planetary rollers 412 come into contact with theinner periphery of the ring roller 413 at their outer sides, and withthe outer periphery of the sun roller 411 at their inner sides. Thus,the planetary carrier equipped with the pins 417 functions to rotatablyretain the intervals among the planetary rollers 412 and to extract therevolution components of the planetary rollers 412.

[0247] In addition, spacers 421 a and 421 b of annular shape arearranged on both end faces of the ring roller 413. A partition plate 422is arranged at the end of the sun roller 411 to separate the spaceaccommodating the sun roller 411 from the internal space of the outputshaft portion 416.

[0248] This simple planetary roller mechanism 402 is assembled, forexample, in a manner as follows:

[0249] Initially, the planetary rollers 412 are mounted on the outerperipheries of the pins 417 of the planetary carrier 415 via the needlebearings 419. Then, the planetary rollers 412 as-mounted are put intoexternal contact with the outer periphery of the sun roller 411. In thatstate, the ring roller 413 is heated to expand, and the planetaryrollers 412 retained by the planetary carrier 415 are inserted into thebore of the ring roller 413. This subsequently cools to complete thesimple planetary roller mechanism 402 in which the ring roller 413 andthe planetary roller 412, as well as the planetary rollers 412 and thesun roller 411, are in contact with each other at a given contactpressure.

[0250] Incidentally, the examples of FIG. 18-20 to be described lateralso have a simple planetary roller mechanism of pin type. [NoiseMeasurement Test]

[0251] Turning to the data for objective representation of the presentinvention's effectiveness, description will be given of the results ofthe noise measurement test made on the above two embodiments of thepresent invention, i.e., the geared motors 101 and 301. Here, the samemeasurement test was also made on several other geared motors for thepurpose of comparison.

[0252] Subjected to the measurement test were six types of gearedmotors, each having a motor and two stages of reduction units.Specifically, each apparatus was coupled to a motor as the externalunit. Six types of first-stage reduction units were prepared includingthe comparative examples. Every second-stage reduction unit was anoscillating internal meshing planetary gear structure.

[0253] Here, description will be directed to the constitutions of thegeared motors prepared as the samples (a) to (f). For the sake ofsimplicity, the combinations of the mechanism parts in the respectivetypes of geared motors are shown by symbols in FIG. 9.

[0254] The following list shows the meanings of the respective symbolsemployed here:

[0255] M . . . Motor;

[0256] C . . . Oscillating Internal meshing planetary gear type;

[0257] F . . . Power-distributed shaft type;

[0258] P . . . Simple planetary type;

[0259] G . . . Gear type; and

[0260] T/D . . . Frictional transmission type by means of rollers.

[0261] More particularly:

[0262] C1 . . . Reduction stage of oscillating internal meshingplanetary gear type (at the subsequent stage=the second stage)

[0263] C2 . . . Reduction stage of oscillating internal meshingplanetary gear type (at the preceding stage=the first stage);

[0264] F(G) . . . Power-distributed-shaft type reduction stage ofgearing system;

[0265] F(T/D) . . . Power-distributed-shaft type reduction stage offrictional transmission roller system;

[0266] P(G) . . . Planetary type reduction stage of gearing system;

[0267] P(T/D) . . . Planetary type reduction stage of frictionaltransmission roller system;

[0268] A . . . Type to retain rollers by retainer; and

[0269] B . . . Type to retain rollers by pins.

[0270] [Types of Geared Motors Used in Test]

[0271] The geared motors of the samples (a) to (f) are represented bysymbols as follows:

[0272] Sample (a) . . . “C1+C2+M”;

[0273] Sample (b) . . . “C1+F(G)+M”;

[0274] Sample (c) . . . “C1+F(T/D)+M”;

[0275] Sample (d) . . . “C1+P(G)+M”;

[0276] Sample (e) . . . “C1+P(T/D)A+M”; and

[0277] Sample (f) . . . “C1+P(T/D)B+M.”

[0278] Of these, the samples (a) to (d) are the geared motors preparedas the comparative examples, and the samples (e) and (f) are the gearedmotors of the embodiments of the present invention.

[0279] The geared motor according to the sample (a), or “C1+C2+M,” takesthe form of a geared motor 600 shown in FIG. 25. This geared motor 600has an oscillating internal meshing planetary gear mechanism 601 (C2) asthe first-stage reduction unit and an oscillating internal meshingplanetary gear mechanism 602 (C1) at the second-stage reduction unit.The input shaft of the first-stage oscillating internal meshing gearmechanism 601 is put into floating connection with the shaft of themotor 603 (M) via a spline 605. The output shaft of the first-stageoscillating internal meshing planetary gear mechanism 601 is put intofloating connection with the input shaft of the second-stage oscillatinginternal meshing planetary gear mechanism 602 via a spline 604.

[0280] The geared motor according to the sample (b), or “C1+F(G)+M),”takes the form of a geared motor 700 shown in FIG. 26. This geared motor700 is formed by replacing “the fiction rollers (the sun roller 511 andthe power-distributed rollers 512)” of FIG. 23 with “gears (a sun gear711 and power-distributed gears 712).” In other words, the geared motor700 is constituted so that its oscillating internal meshing planetarygear mechanism 751 (C1) of power-distributed shaft type is supplied withinput rotations from a gear transmission mechanism 752 [F(G)] comprisedof the sun gear 711 and the power-distributed gears 712. The input shaft702 having the sun gear 711 on its extremity is put into splineconnection with the shaft 701 of the motor 753 (M).

[0281] The geared motor according to the sample (c), or “C1+F(T/D)+M,”is the conventional geared motor 500 shown in FIG. 23. In this gearedmotor 500, the power-distributed shafts is supplied with input rotationsfrom the transmission mechanism of friction roller type [F(T/D)].

[0282] The geared motor according to the sample (d), or “C1+P(G)+M,”takes the form of a geared motor 800 shown in FIG. 27. This geared motor800 has a planetary gear mechanism 801 [P(G)] as the first-stagereduction unit and an oscillating internal meshing planetary gearmechanism 802 (C1) as the second-stage reduction unit. Floatingconnection structures are established in both the coupling portion 805between the input shaft of the planetary gear mechanism 801 and theoutput shaft of the motor 803 (M) and the coupling portion 804 betweenthe output shaft of the planetary gear mechanism 801 and the input shaftof the oscillating internal meshing planetary gear mechanism 802.

[0283] The geared motor of the sample (e), or “C1+P(T/D)A+M,” is thegeared motor 101 shown in FIG. 1, according to the first embodiment ofthe present invention. This geared motor 101 has the simple planetaryroller mechanism 202 as the frictional transmission unit 201, andretains the planetary rollers 212 by the retainer arranged on theplanetary carrier 215.

[0284] The geared motor of the sample (f), or “C1+(T/D)B+M,” is thegeared motor 301 shown in FIG. 6, according to the second embodiment ofthe present invention. This geared motor 301 has the simple planetaryroller mechanism 402 as the frictional transmission unit 304, andretains the planetary rollers 412 by the pins arranged on the planetarycarrier 415.

[0285] [Test Conditions and Method]

[0286] The following conditions and method were employed for themeasurement test.

[0287] (1) Measurement was made at both no load and 100% load.

[0288] (2) Before measurement, each sample was run in for two minutesclockwise and two minutes counterclockwise regardless of its lubricatingsystem.

[0289] (3) Measurement rotations both clockwise and counterclockwise.

[0290] (4) Measurements were obtained from five microphones placed onemeter off from surfaces of the geared motor, namely, the surfaces on theupper, left, and right sides of the geared motor, in front of thelow-speed shaft, and on the back of the motor (the one meter excludingany projection).

[0291] (5) Microphone selector was switched to read measurements from aprecision noise meter on a one-place-at-a-time basis.

[0292] (6) Measurement was made in a soundproof chamber.

[0293] (7) The samples were mounted on a lightweight base of lowerrigidity (flimsy or less rigid base), assuming harsh installationconditions. Some of the samples were also mounted on an FC surface plate(cast iron foundation) for measurement. In either case, the samples werebrought into intimate contact with the top surface of the base or thesurface plate so as not to create a space therebetween.

[0294] (8) Prony brake as the load.

[0295] (9) Audibility A-weighted.

[0296] (10) The outputs of the noise meter were subjected to FFTanalysis for noise spectrum measurement. At 32-times SUM (averaging)mode.

[0297] [Noise Measurements]

[0298] The noise measurements are shown in the table of FIG. 10 in theform of numerals. The differences in noise level at 100% load are shownin the graph of FIG. 11. FIGS. 12 to 15 show the noise spectrumanalyses.

[0299] [Considerations from Noise Measurements]

[0300] The noise measurements allow the following considerations.

[0301] (1) With reference to the geared motor (a), the gearing-systemedgeared motor (b) of power-distributed type was higher in noise. Thereason for this seems to be that the latter, because of being thepower-distributed type, caused the mutual transmission of vibrationsthrough its power-distributed shafts, thereby producing overallresonance.

[0302] (2) It is found from a comparison between the power-distributedtypes that the sample (c), having the power-distributed transmissionsystem replaced with the friction roller type, was lower in noise thanthe sample (b). The reason for this seems to be that the contactsurfaces of the friction rollers appropriately exerted their vibrationabsorbing functions. The friction roller type, however, made littledifference from the type (a). This means that the simple use of frictionrollers does not always offer the noise reduction effect.

[0303] (3) It is seen that the geared motor (d), employing a planetarygear mechanism at the preceding stage, was remarkably high in noise ascompared to the types (a) to (c). The reason for this seems to be thatthe planetary gear mechanism itself included a number of gear-meshingpoints, and those number of meshing points produced vibrations to boostthe overall noise level. This means that just interposing thesimple-planetary-typed reduction unit offers no noise reduction effect,and may even cause a noise increase.

[0304] (4) In contrast, it is seen that the geared motors of types (e)and (f) having been described in the embodiments of the presentinvention achieved a great noise reduction as compared to the others.The chief reason for this seems to be that the simple-planetary typesemployed the friction rollers instead of gears. In other words, theplanetary-gear-typed geared motor (d), because of being the planetarytype, was inevitably greater in the number of meshing points among itsgears to produce extremely higher noises. On the contrary, the gearedmotors of types (e) and (f) had replaced the gears with the frictionrollers, and therefore a number of frictional contact surfaces weresecured instead, which enhanced the noise absorbing function to achievethe overall noise reduction.

[0305] (5) Now, what is responsible for the difference between the type(c) and the types (e), (f) seems to be that: while the power-distributedroller type (c) could secure frictional contact surfaces as many as thetypes (e) and (f) did, the frictional contact surfaces rather functionedto pick up the vibrations of the power-distributed shafts (as describedabove) to hinder the high noise-reduction effect. In contrast, itappears that the types (e) and (f), because of being the simpleplanetary type, had no possibility of picking up unnecessary vibrationsand thus could contribute to the noise reduction.

[0306] (6) When the mountings were switched from the lightweight basesto the surface plates, the type (a) underwent a significant change whilethe types (e) and (f) did not make a very large change in noise level.This fact allows the following reasoning. That is, the geared motor oftype (a) itself has a considerable level of vibrations, and thereforewhen the motor is mounted on a lightweight base, the base is vibrated bythe motor to produce higher noises (through resonance). In contrast,when this motor is mounted on a mating member extremely robust in termsof rigidity, such as a surface plate, those vibrations are suppressedbecause of the mounting, thereby reducing the noises. Meanwhile, thegeared motors of types (e) and (f) themselves are controlled invibration level by a fair amount, and thus make little differencedepending on the modes of installation or the mating member for theinstallation.

[0307] In any case (regardless of whether the above reasoning is corrector not), it is at least apparent that the vibration reducing effectprevails throughout the geared motors (e) and (f) of the presentinvention to the extent that the difference in the mode of installationproduces little difference in noise level. In view of the fact that ageared motor of this type needs to be mounted on some mating member inactual applications, it is a tremendous advantage to be “low in noiselevel regardless of the mating member.”

[0308] (7) As also seen from the noise spectra, the geared motors (e)and (f) were much reduced in noise level almost all over the frequencydomains as compared to the other geared motors (a) to (d). This suggeststhat great reductions were made both in noise, which is easy to perceiveat higher frequencies, and in vibration, which is easy to perceive atlower frequencies.

[0309] Hereinafter, description will be given of the specific variationsfor practicing the present invention.

[0310] Each of the above-described embodiments has dealt with the casewhere the joint casing 153, 353 comprises a part of the casing 151, 351of the reduction gear unit 102, 302 and a part of the casing 155, 355 ofthe motor unit 103, 303, so that the simple planetary roller mechanism202, 402 serving as the frictional transmission unit 104, 304 isarranged inside the joint casing 153, 353 in order to ensure the unityas a geared motor.

[0311] However, as far as further “noise reduction” is intended, thecasings of the reduction gear unit, frictional transmission unit, andmotor unit may be deliberately separated from each other in order toblock vibrations being transmitted across units through the casings.

[0312] In this case, some vibration absorbing means, such as rubber, canbe inserted into the coupling portions among the casings to achievefurther blockage of vibration transmission.

[0313] For the purpose of avoiding outward vibration transmissionthrough the casings, it is also preferable that the direct fixingbetween the ring roller 213, 413 of the simple planetary rollermechanism 202, 402 and the joint casing 153, 353 be abandoned, andvibration absorbing means or a space be interposed between the twomembers.

[0314] By so doing, the three units, namely, the reduction gear unit,the frictional transmission unit, and the motor unit can be insulatedfrom one another in terms of the power transmission paths as well as inview of the casings. This particularly suppresses casing vibrations,thereby improving the effect of avoiding the resonance with matingmembers as well as among the units. In this connection, when the threecasings are separated from one another, the geared motor's legs for usein external installation are preferably arranged on the casing of thefrictional transmission unit that employs the simple planetary rollermechanism to allow the vibration absorbing function. By this means, thegeared motor installed can make an additional suppression of thevibration transmission to the mating member, thereby allowing a furtherreduction in noise level.

[0315] The embodiments described above have dealt with the cases wherethe sun rollers 211, 411 of the simple planetary roller mechanisms 202,402 make the input elements, the planetary carriers 215, 415 supportingthe planetary rollers 212, 412 the output elements, and the ring rollers213, 413 the fixed elements. However, the input, output, and fixedelements create the six combinations as shown in FIG. 16, and any ofthese may be selected if needed. These input-output-fixed combinationscan be combined with variations of roller diameters to develop a seriesof driving apparatuses with a great variety of reduction ratios andfunctions.

[0316] That is, due to its structure, an oscillating internal meshingplanetary gear unit is composed of special parts. Keeping many varietiesof parts in stock all the time leads to higher inventory costs, which isone of the big problems to the fabricator side. Meanwhile, a frictionaltransmission unit can be easily modified in speed change ratio bychanging the diameter of each friction roller. In addition, a frictionaltransmission unit can secure an extremely wide range of speed changeratio variations, including step-ups, by switching theinput-output-fixed combination. Moreover, since each of its frictionrollers is capable of stepless changes in diameter, a frictionaltransmission unit is also widely applicable to yet finer adjustments inspeed change ratio. Accordingly, this frictional transmission unit cancarry a variety of functions to secure variety of the entire drivingapparatus (even when using the same oscillating internal meshingplanetary gear unit and/or the same motor). Therefore, a frictionaltransmission unit is highly advantageous in developing a series ofdriving apparatuses.

[0317] Now, though including some repetitions, description will be madein detail of the above-mentioned contrivances as to the arrangement andassembly of the first reduction mechanism unit (thefrictionally-engaging unit) 104. These contrivances are particularlyeffective at practicing the present invention while minimizing thechanges to the conventional driving apparatuses.

[0318] Returning to FIG. 1, the support carrier 123 closer to the driveunit 103 is of annular shape having the center hole 123 a. Inside thiscenter hole 123 a lies the extremity 111 a of the first shaft 111. Theother support carrier 124 is integrally formed on the base of the secondshaft 112, and has the recess 124 a into which the other end 111 b ofthe first shaft 111 is inserted. The first shaft 111 is rotatablysupported by the bearing 133 fitted into the through hole 123 a in thecarrier 123, and the bearing 134 fitted to the vicinity of the recess124 a in the other support carrier 124.

[0319] As shown in FIGS. 2 and 3, the first reduction mechanism unit 104is of simple planetary roller structure, including the sun roller 211,the planetary rollers 212, the ring roller 213, and the planetarycarrier 215. The sun roller 211 is to be coupled to the drive shaft(motor shaft) 161 of the drive unit 103. The planetary rollers 212 makerolling contact with the outer periphery of the sun roller 211. Theplanetary rollers 212 also make internal contact with the ring roller213. The planetary carrier 215 extracts the revolution components of theplanetary rollers 212 and transmits the same to the first shaft 111 ofthe second reduction mechanism unit (the oscillating internal meshingplanetary gear unit) 102.

[0320] The outside diameter of the ring roller 213 in this firstreduction mechanism 104 is set within the outside diameter of thebearing 131 that supports the one closer to the drive unit 103, of thepair of support carriers 123 and 124 in the second reduction mechanismunit 102 (namely, the support carrier 123). Besides, the ring roller 213is situated within the casing 151 (more specifically, within the jointcasing 153), in the space on the drive-unit-103 side of the bearing 131.

[0321] The inside diameter D3 of the ring roller 213 is set to besomewhat smaller than the sum of the value twice the diameter D2 of theabove-mentioned planetary rollers 212 and the diameter D1 of the sunroller 211. Therefore, when the ring roller 213 has the planetaryrollers 212 and the sun roller 211 arranged inside, the ring roller 213undergoes a subtle elastic deformation toward the radial outside. It isthe stresses accompanying this deformation that apply a given pressingforce to the contact surfaces among the respective fiction rollers 211,212, and 213 to generate frictional forces.

[0322] The ring roller 213 is fixed to the joint casing 153 by thethrough bolts 252, making the fixed element of the simple planetaryroller structure. Here, the sun roller 211 makes the input element, andthe planetary carrier 215 supporting the planetary rollers 212 makes theoutput element. To prevent radial external pressures from acing on thering roller 213, the outside diameter of the ring roller 213 is set tobe smaller than the bore diameter of the joint casing 153.

[0323] The planetary carrier 215 for extracting the revolutions of theplanetary rollers 212 has the output shaft portion 216 of hollowcylindrical shape, projected toward the reduction gear unit 102, and theretainer portion (the retainer) 217 integrally formed on the base sideof the output shaft portion 216. The inner spline 218 is formed on theinner periphery of the output shaft portion 216. This inner spline 218engages with the outer spline formed on the shaft end portion of thefirst shaft 111 of the second reduction mechanism unit 102 (see FIG. 1),making integral rotations with the same.

[0324] The retainer portion 217 has four axially-extending projections217 a to 217 d to be inserted to between the four planetary rollers 212.Each of the projections 217 a to 217 d is provided with concave arcuatesurfaces 219 having the same curvature as that of the outer peripheriesof the planetary rollers 212.

[0325] Thus, the retainer portion 217 puts the above-mentioned concavearcuate surfaces 219 into contact with the planetary rollers 212 toretain the respective planetary rollers 212 in regular mutual positionsalong the circumferential direction at 90° intervals. As a result, theplanetary carrier 215 equipped with this retainer portion 217 functionsto rotatably retain the planetary rollers 212 and to extract therevolution components of the planetary rollers 212.

[0326] On both end faces of the ring roller 213 are arranged the sideplates 221 of annular shape. By these side plates, the contact surfaceof the ring roller 213 with the planetary rollers 212 is shielded fromoutside all over the circumference. This shielded space is also sealedfrom inside by the outer peripheries of the retailer portion 217 so thattraction grease priced higher than gear grease is enclosed in theshielded space. The role of the traction grease is to ensure frictionalforces, not to reduce friction.

[0327] The partition plate 222 is also arranged at the end of the sunroller 211 to separate the space accommodating the sun roller 211 fromthe internal space of the output shaft portion 216.

[0328] Note that the simple planetary roller structure for the firstreduction mechanism unit according to the present invention is notlimited to the retainer type as described above. The structure may alsobe of pin type in which the planetary carrier 215 has axially-extendingpins so that the planetary rollers 212 of annular shape are rotatablyretained by the pins.

[0329] In this first reduction mechanism unit 104, the drive unit 103drives the sun roller 211, which urges the planetary rollers 212 torevolve around the sun roller 211. Since they are sandwiched between thering roller 213 and the sun roller 212, the planetary rollers 212 rollover the inner periphery of the ring roller 213 while revolving aroundthe sun roller 211. In other words, the planetary rollers 212 entailtheir own rotations while revolving around the sun roller 211. Therevolutions of the planetary rollers 212 are extracted by the planetarycarrier 215 via the retainer portion 217 and transmitted to the firstshaft of the second reduction mechanism unit 102 at a given reductionratio. Incidentally, the planetary carrier 215 and the first shaft ofthe second reduction mechanism unit 102 may be integrated with eachother.

[0330] Then, as described previously, the rotations are transmittedthrough the second reduction mechanism unit 102 of oscillating internalmeshing planetary gear structure at a given reduction ratio, and outputfrom the second shaft 112.

[0331] Here, the present inventors have focused on the fact that thering roller 213 in the simple planetary roller structure has the samering configuration as that of the bearing 131, and found that a littlechange to the internal design of the casing 151 makes the firstreduction mechanism unit 104 installable to rational positions near thebearing 131. Under this idea, the outside diameter of the ring roller213 is set to be within that of the bearing 131 for supporting thesupport carrier 123 in the second reduction mechanism unit 102. Thisallows the ring roller 213 to be concentrically accommodated at the sidecloser to the drive unit 103, of the ring roller 213.

[0332] As a result, the first-stage reduction mechanism unit achieveshigher reduction ratios (higher outputs) considering its simpleplanetary structure, whereas the driving apparatus 101 in thisembodiment is controlled within mere 5% or so in axial extension ascompared to a driving apparatus consisting of the drive unit 103 and thesecond reduction mechanism unit 101 only. Therefore, the contradictorydemands for higher reduction ratios and more compact configurations canbe rationally satisfied at the same time, which has been regarded asdifficult. This also reduces the manufacturing costs greatly as comparedto the conventional ones.

[0333] Moreover, the first reduction mechanism unit 104 employs thesimple planetary roller structure of frictional transmission type inwhich the rotational power is transmitted by means of the frictionalforces produced among the friction rollers 211, 212, and 213. Therefore,the first reduction mechanism unit 104 is quieter as compared to thatconstituted by using a gear structure. Accordingly, despite of itstwo-stage reduction structure having the first and second reductionmechanism unit 104 and 102 in combination, the driving apparatus 101will not produce a problem of increasing noises, but rather contribute anoise reduction by far beyond expectations, as described previously. Inparticular, this driving unit accommodates both the first and secondreduction mechanism units 104 and 102 in the same internal space insideits casing 151. This precludes individual resonance in the two spacesfrom interfering with each other for generation of new resonance,thereby avoiding a further increase in noise.

[0334] Now, with reference to FIGS. 17(A) to 17(C), description will begiven of the method for assembling (manufacturing) the driving apparatus101.

[0335] As shown in FIG. 17(A), the casing 151 (more specifically, thejoint casing 153 constituting the same) is initially attached to thedrive unit 103. In other words, the drive unit 103 as assembled andmodularized in a previous step is coupled to the casing 151.

[0336] Then, as shown in FIG. 17(B), the first reduction mechanism unit104 of simple planetary roller structure is mounted, from the sideopposite from (the side opposite to) the drive unit 103, onto the casing151 (the joint casing 153) having the drive unit 103 attached thereto.This first reduction mechanism unit 104 has been assembled in a previousstep by shrink-fitting the sun roller 211, the planetary rollers 212,and the ring roller 213, and then inserting the retainer portion 217 ofthe planetary carrier 215 to the same. Therefore, the entire unit hasonly to be inserted into the casing 151 before the ring roller 213 isfixed thereto by the through bolts 252.

[0337] Here, this first reduction mechanism unit 104 can be readilyinserted because the sun roller 211 and the drive shaft 161 are in afloating coupling structure (spline structure) with each other, creatingradial play therebetween.

[0338] Subsequently, as shown in FIG. 17(C), the second reductionmechanism unit 102 of oscillating internal meshing planetary gearstructure is mounted onto the casing 151 having the first reductionmechanism unit 104 built-in. Again, this second reduction mechanism unit102 (excluding the internal gear 120) can be assembled up to nearly oneunit (one module) in a previous step, and therefore has only to beinserted into the casing 151. Incidentally, the internal gear 120 (andthe central casing 152 containing the same) is preferably fixed to thejoint casing 153 in advance.

[0339] Then, the front casing 154 is mounted to complete the drivingapparatus 101.

[0340] According to this method, the high-modularitied units, namely,the drive unit 103, the first reduction mechanism unit 104, and thesecond reduction mechanism unit 102, can be combined quickly on thebasis of the casing 151 (the joint casing 153). This advantage isattributed to the fact that the outside diameter of the first reductionmechanism unit 104 (the outside diameter of the ring roller 213) is setto be smaller than the outside diameter of the bearing 131 in the secondreduction mechanism unit 102 so that these units are accommodated in thesame internal space.

[0341] Moreover, the first and second reduction mechanism units 104 and102 both of coaxial power transmission configuration can be mounted withreference to the axis center of the drive shaft 161 of the drive unit103 mounted first. This facilitates the center positioning, and therebyimproves the assembling precision and the assembling speed greatly.

[0342] As a result, the worker's trouble for the assembly is largelyeased, and the manufacturing costs are also reduced.

[0343] The foregoing embodiments have dealt with the cases where thesecond reduction mechanism unit in this driving apparatus is ofoscillating internal meshing planetary gear structure. However, as seenfrom its concept, the present invention is not limited to theabove-mentioned structure. That is, the present invention is similarlyapplicable with any other second reduction mechanism unit as long as theunit is of support carrier transmission type structure, comprising aspeed reducer to be coupled to the first reduction mechanism unit, and apair of support carriers rotatably supported by the casing via bearingsto extract the rotating power of the reduction device.

[0344] Finally, with reference to the embodiment shown in FIGS. 18 to20, description will be made in detail of the structure for mounting thefrictional transmission unit 104 by using the “mounting referencesurface” (and in detail of the floating connection structure).Incidentally, this embodiment basically includes a number of componentscommon to those of the embodiment shown in FIGS. 1 to 4. Accordingly,like components will be designated by reference numerals having the samelower two digits, and repetitive descriptions thereto will be omitted.

[0345] This single planetary roller mechanism 202 is mounted onto adeeply-bored recess portion 251 formed in the inner periphery of a jointcasing 153 at the side closer to a reduction gear unit 102. Here, theinside diameter of this recess portion 251 is set to be smaller thanthat of an accommodating portion 253 for accommodating a bearing 131, sothat the difference in inside diameter forms a shoulder 260 on the jointcasing 153. An end face of the bearing 131 is put into contact with theshoulder 260 to set the center axis L of the bearing 131 in position.

[0346] As shown in FIGS. 19 and 20, the simple planetary rollermechanism 202 has friction rollers consisting of a sun roller 211, aplurality (four, in this embodiment) of planetary rollers 212, and aring roller 213. The sun roller 211 has a spline shaft portion 214. Theplanetary rollers 212 are of hollow cylindrical shape, and make rollingcontact with the outer periphery of the sun roller 211. The ring roller213 has an inside diameter D3 somewhat smaller than the sum of thediameter D1 of the sun roller 211 and the value twice the diameter D2 ofthe above-mentioned planetary rollers 212. The ring roller 213 has theplanetary rollers 212 arranged inside so as to make internal contact.

[0347] Again, the ring roller 213 makes the fixed element of the simpleplanetary roller mechanism 202. The sun roller 211 makes the inputelement, and a planetary carrier 215 supporting the planetary rollers212 the output element.

[0348] On the bottom of the recess portion 251 in the joint casing 153is formed a mounting reference surface 261 which is perpendicular to thedirection of the rotation/revolution axes of the sun roller 211, theplanetary rollers 212, and the ring roller 213 (the direction of thecenter axis L). The ring roller 213 is pressed against this mountingreference surface 261 to be fixed to the joint casing 153. As for themeans for pressing the ring roller 213 against the mounting referencesurface 261 in the present embodiment, the ring roller 213 is providedwith bolt holes 262 piercing therethrough in the direction of therotational axis (the direction of the center axis L. The ring roller 213is fixed to the mounting reference surface 261 by fixing bolts 252inserted through the bolt holes 262 and threadedly engaged with tappedholes 263 formed in the mounting reference surface 261.

[0349] Incidentally, the present invention may also use any pressingmeans other than the above-described pressing means.

[0350] The inside diameter of the recess portion 251 is set to besomewhat greater than the outside diameter of the ring roller 213.Besides, the inside diameter of the bolt holes 262 is set to be greaterthat the outside diameter of the fixing bolts 252. Accordingly, the ringroller 213 and the fixing bolts 252 are fitted to the recess portion 251and the bolt holes 262 with play, respectively. The ring roller 213 canbe shifted within the range of the play before the fixing bolts 252 aretightened completely. This makes the ring roller 213 (the simpleplanetary roller mechanism 202) adjustable in axis position within themounting reference surface 261.

[0351] As shown in FIG. 19, the planetary carrier 215 for extracting therevolutions of the planetary rollers 212 has an annular flange portion215A, an output shaft portion 216 of hollow cylindrical shape, and fourpins 217. The output shaft portion 216 is projected from the flangeportion 215A toward the reduction gear unit 102. The pins 217 are fittedand fixed to the flange portion 415 a at their bases, and projectedtoward a motor unit 103 at their extremities. Cylindrical inner rollers264 are arranged on the pins 217 so as to be capable of slidingrotations.

[0352] Each of the planetary rollers 212 has a center hole 212A formedin its axis position. By means of the center holes 212A and through theintervention of the inner rollers 264, the planetary rollers 212 arerotatably fitted on the outer peripheries of the respective pins 217,whereby the planetary rollers 212 are retained at constant mutualpositions. In this state, the outer periphery of each of the planetaryrollers 212 is in contact with the inner peripheral surface of the ringroller 213 and with the outer peripheral surface of the sun roller 211.Thus, the planetary carrier 215 provided with the pins 217 functions tomaintain the spacing among the planetary rollers and 212 to extract therevolution components of the planetary rollers 212.

[0353] The inner rollers 264 make rotations while sliding at the contactsurfaces with the outer peripheral surfaces of the pins 217 and with thecenter holes 212A, so as to absorb the difference in rotational speedbetween the pins 217 and the planetary rollers 212. That is, thecylindrical inner rollers 264 make rotations faster than the rotational(revolving) speed of the pins 217 and slower than the rotating speed ofthe planetary rollers 212. This allow the respective contact surfaces toslide at a speed smaller than the actual difference in speed between thepins 217 and the planetary rollers 212. As a result, it becomes possibleto reduce the frictional heat generation, the frictional resistance, andthe like.

[0354] On both sides of the planetary rollers 212 are arranged annularspacers 221A and 221B.

[0355] The output shaft portion 216 of the planetary carrier 215 alsohas a carrier-side shaft insertion hole 265 formed in its axis position.A first shaft 111 can be inserted to the carrier-side shaft insertionhole 265 so that the planetary carrier 215 engages with the first shaft111 in the rotational direction to make integral rotations.Specifically, this carrier-side shaft insertion hole 265 has an innerspline structure to establish floating connection with the first shaft111 in the rotational direction while allowing a constant radialclearance (play).

[0356] Meanwhile, the sun roller 211 has a sun-roller-side shaftinsertion hole 266 formed in its axis position. A motor shaft 161 of themotor unit 103 can be inserted to the sun-roller-side shaft insertionhole 266 so that the sun roller 211 engages with the motor shaft 161 inthe rotational direction to make integral rotations. Specifically, thissun-roller-side shaft insertion hole 266 has an inner spline structureto establish floating connection with the motor shaft 161 in therotational direction while allowing a constant radial clearance (play).

[0357] The entire frictional transmission unit 104, having thesun-roller-side shaft insertion hole 266 formed in the sun roller 211and the carrier-side shaft insertion hole 265 formed in the planetarycarrier 215, therefore forms a so-called shaft coupling structure.

[0358] This simple planetary roller mechanism 202 is assembled, forexample, in the following manner. Initially, the planetary rollers 212are mounted on the outer peripheries of the pins 217 of the planetarycarrier 215 via the cylindrical inner rollers 264. Then, the planetaryrollers 212 as-mounted are put into external contact with the outerperiphery of the sun roller 211. In that state, the ring roller 213 isheated to expand, and the planetary rollers 212 retained by theplanetary carrier 215 are inserted into the bore of the ring roller 213.This subsequently cools to complete the simple planetary rollermechanism 202 in which the ring roller 213 and the planetary rollers212, as well as the planetary rollers 212 and the sun roller 211, are incontact with each other at a given contact pressure.

[0359] In its mounting onto a casing, the simple planetary rollermechanism 202 is mounted onto the mounting reference surface 261 asmentioned previously. This mounting is carried out with the motor unit103 previously installed on the casing 153. Therefore, the simpleplanetary roller mechanism 202 is brought into the recess portion 251 sothat the motor shaft 161 is inserted into the sun-roller-side shaftinsertion hole 266. This simple planetary roller mechanism 202 isshifted within the mounting reference surface 261 in order that the axesof the sun-roller-side shaft insertion hole 266 and the motor shaft 161coincide with each other. After the adjustment is completed with aconstant circumferential clearance (play) between the sun-roller-sideshaft insertion hole 266 and the motor shaft 161, the ring roller 213 isfixed by the fixing bolts 252. Then, the reduction gear unit 102 ismounted so that the output shaft portion 216 of the planetary carrier215 of the simple planetary roller mechanism 202 lies inside a centerhole 123 a in the support carrier 123 of the reduction gear unit 102.This completes a geared motor 101.

[0360] The ring roller 213 of this simple planetary roller mechanism 202is fixed to the joint casing 153. Accordingly, unlike ordinary couplingsas shown in FIGS. 22 and 23, which are simply fitted onto shafts to keeptheir own positions (by being supported by the shafts in return), thering roller 213 can maintain a given amount of clearance between eachpower transmission shaft (the motor shaft 161, the first shaft 111) andthe corresponding shaft insertion hole 265, 266 all the time. Thisensures the blockage and absorption of vibrations and noises. Moreover,since the simple planetary roller mechanism 202 is adjustable in axisposition, those clearances can be precisely set in the first place. Thisis combined with the ensured blockage and absorption to achieve furthersuppression of noises and vibrations.

[0361] Furthermore, in this geared motor 101, the ring roller 213 isfixed to the joint casing 153 without undergoing radial pressures, i.e.,as pressed against the mounting reference surface 261 which isperpendicular to the center axis L. Accordingly, as compared to thecases where the ring roller 213 is fixed by press-fit or other method,the contact pressures among the friction rollers are prevented fromfluctuation. Therefore, smooth rotations/revolutions of the planetaryrollers 212 and the sun roller 211 are realized. In addition, the ringroller 213 allows its own vibrations to some extent to realize energyabsorption there. At the same time, the mounting reference surface,which is formed along the direction of thickness of the joint casing 153and therefore high in radial rigidity, can surely receive the vibrationsto prevent the vibrations from being transmitted to the entire casing.

[0362] The above-described method of fixing the ring roller 213 ishighly advantageous in view of noise suppression as previouslydescribed. In addition to achieving the simple noise reduction, themethod also eliminates the need for the press-fitting of the ring roller213 as also described in the foregoing embodiments, and therebyfacilitates the assembling processes.

[0363] The simple planetary roller mechanism 202 provides each of theplanetary carrier 215 and the sun roller 211 with a shaft insertion holeto establish a “shaft coupling structure.” Therefore, this simpleplanetary roller mechanism 202 can be replaced with an ordinary couplingthat has so far coupled the motor shaft 171 and the first shaft 111directly, to realize this geared motor 101 easily (though needed a smallchange to the casings). The simple planetary roller mechanism 202 canalso be realized into an axially compact configuration, causing no largeincrease in the axial size of the entire geared motor 101.

[0364] While the present embodiment has dealt with the case where thering roller 213 is directly fixed to the mounting reference surface 261,the present invention is not limited thereto. The essential function ofthis mounting reference surface is to determine the position to fix thering roller. Therefore, the present invention also covers suchconfigurations that the ring roller is pressed against the mountingreference surface for positioning and then fixed by another part of thecasing. Put another way, the present invention generally covers suchconfigurations that the ring roller is positioned not only at itsouter-periphery side (by press-fit or other means) but at its end-faceside as well, and mounted so that external forces radially acting on thering roller are not directly transmitted in the direction of thicknessof the casing.

[0365] While there has been described what are at present considered tobe preferred embodiments of the invention, it will be understood thatvarious modifications may be made thereto, and it is intended that theappended claims cover all such modifications as fall within the truespirit and scope of the invention.

[0366] Moreover, the individual configurations set forth in therespective appended claims may be freely combined without departing fromthe spirit thereof, so that the combination offers a synergisticfunction.

What is claimed is:
 1. A driving apparatus comprising an oscillatinginternal meshing planetary gear unit having an internal gear and anexternal gear making internal contact with said internal gear, thecenter of said internal gear lying inside the periphery of said externalgear, and an external unit to be connected with said oscillatinginternal meshing planetary gear unit so as to be capable of inputting orextracting power thereto or therefrom, wherein: between said oscillatinginternal meshing planetary gear unit and said external unit isinterposed a frictional transmission unit which has a plurality offriction rollers contacting each other, for transmitting rotationalpower between said oscillating internal meshing planetary gear unit andsaid external unit by means of friction among said plurality of frictionrollers; and said frictional transmission unit is constituted by asimple planetary roller mechanism including said friction rollersincluding a sun roller, a plurality of planetary rollers being retainedby a planetary carrier and making rolling contact with the outerperiphery of said sun roller, and a ring roller with which saidplurality of planetary rollers make internal contact.
 2. The drivingapparatus according to claim 1, wherein said planetary carrier in saidsimple planetary roller mechanism has a retainer for occupying spacesaround said plurality of planetary rollers to retain said planetaryrollers at constant mutual positions.
 3. The driving apparatus accordingto claim 1, wherein said planetary carrier in said simple planetaryroller mechanism has pins for penetrating through the respective centersof said planetary rollers to retain said planetary rollers at constantmutual positions.
 4. The driving apparatus according to claim 1,wherein: said ring roller in said simple planetary roller mechanism isfixed; and either said planetary carrier retaining said plurality ofplanetary rollers or said sun roller makes an input side, and theremaining makes an output side.
 5. The driving apparatus according toclaim 1, wherein: said external unit is a motor unit for supplying arotational input to said oscillating internal meshing planetary gearunit; said frictional transmission unit is interposed between a driveshaft of said motor unit and said oscillating internal meshing planetarygear unit; and said oscillating internal meshing planetary gear unit andsaid motor unit are integrally connected with each other by a jointcasing comprising parts of the casings for these units, said frictionaltransmission unit being arranged inside said joint casing.
 6. Thedriving apparatus according to claim 1, wherein, of the couplingportions between said frictional transmission unit and said oscillatinginternal meshing planetary gear unit and between said frictionaltransmission unit and said external unit, at least one coupling portionhas a floating connection structure.
 7. The driving apparatus accordingto claim 6, wherein, of the coupling portions between said planetarycarrier in said frictional transmission unit of simple planetary rollermechanism and said oscillating internal meshing planetary gear unit andbetween said sun roller and said external unit, at least the couplingportion between said planetary carrier and said oscillating internalmeshing planetary gear unit has said floating connection structure. 8.The driving apparatus according to claim 6, wherein said floatingconnection structure is a spline connection structure.
 9. The drivingapparatus according to claim 1, wherein: a casing for accommodating saidfrictional transmission unit is provided with a mounting referencesurface perpendicular to the direction of the rotation axes of said sunroller, planetary rollers, and ring roller; and the driving apparatusfurther comprises fixing means for fixing said ring roller to saidcasing while pressing said ring roller against the mounting referencesurface.
 10. The driving apparatus according to claim 9, wherein saidring roller is adjustable in axis position within the mounting referencesurface.
 11. The driving apparatus according to claim 9, wherein saidsun roller is provided with a sun-roller-side shaft insertion hole intowhich a power transmission shaft of said external unit is insertable,and said planetary carrier is provided with a carrier-side shaftinsertion hole into which a power transmission shaft of said oscillatinginternal meshing planetary gear unit is insertable, so as to form saidfrictional transmission unit into a shaft coupling structure forallowing relative rotations of said power transmission shafts.
 12. Thedriving apparatus according to claim 11, wherein at least either saidsun-roller-side shaft insertion hole or said carrier-side shaftinsertion hole has a floating connection structure with respect to saidpower transmission shaft inserted therethrough.
 13. The drivingapparatus according to claim 9, wherein: said ring roller is providedwith a bolt hole piercing therethrough in the direction of the rotationaxis so that said ring roller is fixable to the mounting referencesurface by a fixing bolt inserted through said bolt hole and threadedlyengaged with a tapped hole formed in the mounting reference surface; andsaid bolt hole has a diameter somewhat greater than that of said fixingbolt so that said ring roller is adjustable in axis position within themounting reference surface as long as said fixing bolt is fitted to saidbolt hole with play.
 14. A driving apparatus comprising: a rotatingshaft to be connected to an external unit; an oscillating internalmeshing planetary gear unit having an internal gear and an external gearmaking internal contact with said internal gear, the center of saidinternal gear lying inside the periphery of said external gear; and africtional transmission unit of simple planetary roller mechanism,having friction rollers including a sun roller, a plurality of planetaryrollers being retained by a planetary carrier and making rolling contactwith the outer periphery of said sun roller, and a ring roller havingsaid planetary rollers arranged inside so as to make internal contact,wherein one of said sun roller, planetary carrier, and ring roller isfixed, either of the other two is coupled to said oscillating internalmeshing planetary gear unit, and the remaining one is coupled to saidrotating shaft.
 15. The driving apparatus according to claim 14,wherein: said ring roller is fixed, said planetary carrier is coupled tosaid oscillating internal meshing planetary gear unit, and said sunroller is coupled to said rotating shaft; and, of the coupling portionsbetween said planetary carrier and said oscillating internal meshingplanetary gear unit and between said sun roller and said rotating shaft,at least one coupling portion has a floating connection structure. 16.The driving apparatus according to claim 14, wherein said oscillatinginternal meshing planetary gear unit has a first shaft and a secondshaft located on the center axis of the driving apparatus, an externalgear being fitted on the outer periphery of said first shaft via aneccentric body so as to be capable of oscillating rotations with respectto said first shaft, an internal gear with which said external gearmeshes internally being provided concentrically with said first shaft,said second shaft being coupled to said external gear via means forextracting only the rotational component of said external gear.
 17. Adriving apparatus comprising a drive unit for generating rotationalpower, a first reduction mechanism unit coupled to an output shaft ofsaid drive unit to transmit the rotational power, and a second reductionmechanism unit of support carrier transmission type, including reductiongears to be coupled to said first reduction mechanism unit, and a pairof support carriers rotatably supported by a casing at both axialoutsides of said reduction gears via bearings, said support carriers forextracting rotational power of said reduction gears, wherein: said firstreduction mechanism unit has a simple planetary roller structure offriction transmission type, including a sun roller to be coupled to saidoutput shaft of said drive unit, a planetary roller making rollingcontact with the outer periphery of said sun roller, a ring roller withwhich said planetary roller makes internal contact, and a planetarycarrier for extracting the revolution component of said planetary rollerand transmitting the same to an input shaft of said second reductionmechanism unit, the outside diameter of said ring roller being setwithin the outside diameter of said bearing supporting thedrive-unit-side support carrier of said pair of support carriers in saidsecond reduction mechanism unit; and said ring roller is situated withinsaid casing, in a space on the drive-unit side of said bearing.
 18. Thedriving apparatus according to 17, wherein said second reductionmechanism unit is constituted as an internal meshing planetary gearmechanism comprising: said input shaft to be connected to said firstreduction mechanism unit; an external gear for making eccentricrotations with respect to said input shaft; an internal gear fixed tosaid casing, said external gear internal meshing with said internalgear; said pair of support carriers rotatably supported by said casingat both axial outside positions of said reduction gears via saidbearings, said support carriers for extracting the rotational componentof said external gear; and an output shaft arranged coaxially with saidinput shaft, the rotations of said support carriers being transmitted tosaid output shaft.
 19. The driving apparatus according to claim 17,wherein: said casing for accommodating said first reduction mechanismunit is provided with a mounting reference surface perpendicular to thedirection of the rotation axes of said sun roller, planetary roller, andring roller; and the driving apparatus further comprises fixing meansfor fixing said ring roller in said space within said casing whilepressing said ring roller against the mounting reference surface. 20.The driving apparatus according to claim 17, wherein said ring roller isadjustable in axis position within the mounting reference surface. 21.The driving apparatus according to claim 17, wherein said sun roller isprovided with a sun-roller-side shaft insertion hole into which saidoutput shaft of said drive unit is insertable, and said planetarycarrier is provided with a carrier-side shaft insertion hole into whichsaid input shaft of said second reduction mechanism unit is insertable,so as to form said first reduction mechanism unit into a shaft couplingstructure for allowing relative rotations of said input and outputshafts.
 22. The driving apparatus according to claim 21, wherein atleast either said sun-roller-side shaft insertion hole or saidcarrier-side shaft insertion hole has a floating connection structurewith respect to said input/output shaft inserted therethrough.
 23. Thedriving apparatus according to claim 17, wherein said ring roller isprovided with a bolt hole piercing therethrough axially so that saidring roller is fixable to a mounting reference surface by a fixing boltinserted through said bolt hole and threadedly engaged with a tappedhole formed in the mounting reference surface; and said bolt hole has adiameter somewhat greater than that of said fixing bolt so that saidring roller is adjustable in axis position within the mounting referencesurface as long as said fixing bolt is fitted to said bolt hole withplay.